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  1.  
  2. /* png.c - location for general purpose libpng functions
  3.  *
  4.  * Last changed in libpng 1.6.2 [April 25, 2013]
  5.  * Copyright (c) 1998-2013 Glenn Randers-Pehrson
  6.  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  7.  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  8.  *
  9.  * This code is released under the libpng license.
  10.  * For conditions of distribution and use, see the disclaimer
  11.  * and license in png.h
  12.  */
  13.  
  14. #include "pngpriv.h"
  15.  
  16. /* Generate a compiler error if there is an old png.h in the search path. */
  17. typedef png_libpng_version_1_6_5 Your_png_h_is_not_version_1_6_5;
  18.  
  19. /* Tells libpng that we have already handled the first "num_bytes" bytes
  20.  * of the PNG file signature.  If the PNG data is embedded into another
  21.  * stream we can set num_bytes = 8 so that libpng will not attempt to read
  22.  * or write any of the magic bytes before it starts on the IHDR.
  23.  */
  24.  
  25. #ifdef PNG_READ_SUPPORTED
  26. void PNGAPI
  27. png_set_sig_bytes(png_structrp png_ptr, int num_bytes)
  28. {
  29.    png_debug(1, "in png_set_sig_bytes");
  30.  
  31.    if (png_ptr == NULL)
  32.       return;
  33.  
  34.    if (num_bytes > 8)
  35.       png_error(png_ptr, "Too many bytes for PNG signature");
  36.  
  37.    png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);
  38. }
  39.  
  40. /* Checks whether the supplied bytes match the PNG signature.  We allow
  41.  * checking less than the full 8-byte signature so that those apps that
  42.  * already read the first few bytes of a file to determine the file type
  43.  * can simply check the remaining bytes for extra assurance.  Returns
  44.  * an integer less than, equal to, or greater than zero if sig is found,
  45.  * respectively, to be less than, to match, or be greater than the correct
  46.  * PNG signature (this is the same behavior as strcmp, memcmp, etc).
  47.  */
  48. int PNGAPI
  49. png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)
  50. {
  51.    png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  52.  
  53.    if (num_to_check > 8)
  54.       num_to_check = 8;
  55.  
  56.    else if (num_to_check < 1)
  57.       return (-1);
  58.  
  59.    if (start > 7)
  60.       return (-1);
  61.  
  62.    if (start + num_to_check > 8)
  63.       num_to_check = 8 - start;
  64.  
  65.    return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check)));
  66. }
  67.  
  68. #endif /* PNG_READ_SUPPORTED */
  69.  
  70. #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  71. /* Function to allocate memory for zlib */
  72. PNG_FUNCTION(voidpf /* PRIVATE */,
  73. png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)
  74. {
  75.    png_alloc_size_t num_bytes = size;
  76.  
  77.    if (png_ptr == NULL)
  78.       return NULL;
  79.  
  80.    if (items >= (~(png_alloc_size_t)0)/size)
  81.    {
  82.       png_warning (png_voidcast(png_structrp, png_ptr),
  83.          "Potential overflow in png_zalloc()");
  84.       return NULL;
  85.    }
  86.  
  87.    num_bytes *= items;
  88.    return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes);
  89. }
  90.  
  91. /* Function to free memory for zlib */
  92. void /* PRIVATE */
  93. png_zfree(voidpf png_ptr, voidpf ptr)
  94. {
  95.    png_free(png_voidcast(png_const_structrp,png_ptr), ptr);
  96. }
  97.  
  98. /* Reset the CRC variable to 32 bits of 1's.  Care must be taken
  99.  * in case CRC is > 32 bits to leave the top bits 0.
  100.  */
  101. void /* PRIVATE */
  102. png_reset_crc(png_structrp png_ptr)
  103. {
  104.    /* The cast is safe because the crc is a 32 bit value. */
  105.    png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);
  106. }
  107.  
  108. /* Calculate the CRC over a section of data.  We can only pass as
  109.  * much data to this routine as the largest single buffer size.  We
  110.  * also check that this data will actually be used before going to the
  111.  * trouble of calculating it.
  112.  */
  113. void /* PRIVATE */
  114. png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)
  115. {
  116.    int need_crc = 1;
  117.  
  118.    if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name))
  119.    {
  120.       if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
  121.           (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
  122.          need_crc = 0;
  123.    }
  124.  
  125.    else /* critical */
  126.    {
  127.       if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
  128.          need_crc = 0;
  129.    }
  130.  
  131.    /* 'uLong' is defined in zlib.h as unsigned long; this means that on some
  132.     * systems it is a 64 bit value.  crc32, however, returns 32 bits so the
  133.     * following cast is safe.  'uInt' may be no more than 16 bits, so it is
  134.     * necessary to perform a loop here.
  135.     */
  136.    if (need_crc && length > 0)
  137.    {
  138.       uLong crc = png_ptr->crc; /* Should never issue a warning */
  139.  
  140.       do
  141.       {
  142.          uInt safe_length = (uInt)length;
  143.          if (safe_length == 0)
  144.             safe_length = (uInt)-1; /* evil, but safe */
  145.  
  146.          crc = crc32(crc, ptr, safe_length);
  147.  
  148.          /* The following should never issue compiler warnings; if they do the
  149.           * target system has characteristics that will probably violate other
  150.           * assumptions within the libpng code.
  151.           */
  152.          ptr += safe_length;
  153.          length -= safe_length;
  154.       }
  155.       while (length > 0);
  156.  
  157.       /* And the following is always safe because the crc is only 32 bits. */
  158.       png_ptr->crc = (png_uint_32)crc;
  159.    }
  160. }
  161.  
  162. /* Check a user supplied version number, called from both read and write
  163.  * functions that create a png_struct.
  164.  */
  165. int
  166. png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)
  167. {
  168.    if (user_png_ver)
  169.    {
  170.       int i = 0;
  171.  
  172.       do
  173.       {
  174.          if (user_png_ver[i] != png_libpng_ver[i])
  175.             png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
  176.       } while (png_libpng_ver[i++]);
  177.    }
  178.  
  179.    else
  180.       png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
  181.  
  182.    if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)
  183.    {
  184.      /* Libpng 0.90 and later are binary incompatible with libpng 0.89, so
  185.       * we must recompile any applications that use any older library version.
  186.       * For versions after libpng 1.0, we will be compatible, so we need
  187.       * only check the first and third digits (note that when we reach version
  188.       * 1.10 we will need to check the fourth symbol, namely user_png_ver[3]).
  189.       */
  190.       if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0] ||
  191.           (user_png_ver[0] == '1' && (user_png_ver[2] != png_libpng_ver[2] ||
  192.           user_png_ver[3] != png_libpng_ver[3])) ||
  193.           (user_png_ver[0] == '0' && user_png_ver[2] < '9'))
  194.       {
  195. #ifdef PNG_WARNINGS_SUPPORTED
  196.          size_t pos = 0;
  197.          char m[128];
  198.  
  199.          pos = png_safecat(m, (sizeof m), pos,
  200.              "Application built with libpng-");
  201.          pos = png_safecat(m, (sizeof m), pos, user_png_ver);
  202.          pos = png_safecat(m, (sizeof m), pos, " but running with ");
  203.          pos = png_safecat(m, (sizeof m), pos, png_libpng_ver);
  204.  
  205.          png_warning(png_ptr, m);
  206. #endif
  207.  
  208. #ifdef PNG_ERROR_NUMBERS_SUPPORTED
  209.          png_ptr->flags = 0;
  210. #endif
  211.  
  212.          return 0;
  213.       }
  214.    }
  215.  
  216.    /* Success return. */
  217.    return 1;
  218. }
  219.  
  220. /* Generic function to create a png_struct for either read or write - this
  221.  * contains the common initialization.
  222.  */
  223. PNG_FUNCTION(png_structp /* PRIVATE */,
  224. png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
  225.     png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
  226.     png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
  227. {
  228.    png_struct create_struct;
  229. #  ifdef PNG_SETJMP_SUPPORTED
  230.       jmp_buf create_jmp_buf;
  231. #  endif
  232.  
  233.    /* This temporary stack-allocated structure is used to provide a place to
  234.     * build enough context to allow the user provided memory allocator (if any)
  235.     * to be called.
  236.     */
  237.    memset(&create_struct, 0, (sizeof create_struct));
  238.  
  239.    /* Added at libpng-1.2.6 */
  240. #  ifdef PNG_USER_LIMITS_SUPPORTED
  241.       create_struct.user_width_max = PNG_USER_WIDTH_MAX;
  242.       create_struct.user_height_max = PNG_USER_HEIGHT_MAX;
  243.  
  244. #     ifdef PNG_USER_CHUNK_CACHE_MAX
  245.          /* Added at libpng-1.2.43 and 1.4.0 */
  246.          create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
  247. #     endif
  248.  
  249. #     ifdef PNG_USER_CHUNK_MALLOC_MAX
  250.          /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
  251.           * in png_struct regardless.
  252.           */
  253.          create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
  254. #     endif
  255. #  endif
  256.  
  257.    /* The following two API calls simply set fields in png_struct, so it is safe
  258.     * to do them now even though error handling is not yet set up.
  259.     */
  260. #  ifdef PNG_USER_MEM_SUPPORTED
  261.       png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn);
  262. #  endif
  263.  
  264.    /* (*error_fn) can return control to the caller after the error_ptr is set,
  265.     * this will result in a memory leak unless the error_fn does something
  266.     * extremely sophisticated.  The design lacks merit but is implicit in the
  267.     * API.
  268.     */
  269.    png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn);
  270.  
  271. #  ifdef PNG_SETJMP_SUPPORTED
  272.       if (!setjmp(create_jmp_buf))
  273.       {
  274.          /* Temporarily fake out the longjmp information until we have
  275.           * successfully completed this function.  This only works if we have
  276.           * setjmp() support compiled in, but it is safe - this stuff should
  277.           * never happen.
  278.           */
  279.          create_struct.jmp_buf_ptr = &create_jmp_buf;
  280.          create_struct.jmp_buf_size = 0; /*stack allocation*/
  281.          create_struct.longjmp_fn = longjmp;
  282. #  else
  283.       {
  284. #  endif
  285.          /* Call the general version checker (shared with read and write code):
  286.           */
  287.          if (png_user_version_check(&create_struct, user_png_ver))
  288.          {
  289.             png_structrp png_ptr = png_voidcast(png_structrp,
  290.                png_malloc_warn(&create_struct, (sizeof *png_ptr)));
  291.  
  292.             if (png_ptr != NULL)
  293.             {
  294.                /* png_ptr->zstream holds a back-pointer to the png_struct, so
  295.                 * this can only be done now:
  296.                 */
  297.                create_struct.zstream.zalloc = png_zalloc;
  298.                create_struct.zstream.zfree = png_zfree;
  299.                create_struct.zstream.opaque = png_ptr;
  300.  
  301. #              ifdef PNG_SETJMP_SUPPORTED
  302.                   /* Eliminate the local error handling: */
  303.                   create_struct.jmp_buf_ptr = NULL;
  304.                   create_struct.jmp_buf_size = 0;
  305.                   create_struct.longjmp_fn = 0;
  306. #              endif
  307.  
  308.                *png_ptr = create_struct;
  309.  
  310.                /* This is the successful return point */
  311.                return png_ptr;
  312.             }
  313.          }
  314.       }
  315.  
  316.    /* A longjmp because of a bug in the application storage allocator or a
  317.     * simple failure to allocate the png_struct.
  318.     */
  319.    return NULL;
  320. }
  321.  
  322. /* Allocate the memory for an info_struct for the application. */
  323. PNG_FUNCTION(png_infop,PNGAPI
  324. png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED)
  325. {
  326.    png_inforp info_ptr;
  327.  
  328.    png_debug(1, "in png_create_info_struct");
  329.  
  330.    if (png_ptr == NULL)
  331.       return NULL;
  332.  
  333.    /* Use the internal API that does not (or at least should not) error out, so
  334.     * that this call always returns ok.  The application typically sets up the
  335.     * error handling *after* creating the info_struct because this is the way it
  336.     * has always been done in 'example.c'.
  337.     */
  338.    info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,
  339.       (sizeof *info_ptr)));
  340.  
  341.    if (info_ptr != NULL)
  342.       memset(info_ptr, 0, (sizeof *info_ptr));
  343.  
  344.    return info_ptr;
  345. }
  346.  
  347. /* This function frees the memory associated with a single info struct.
  348.  * Normally, one would use either png_destroy_read_struct() or
  349.  * png_destroy_write_struct() to free an info struct, but this may be
  350.  * useful for some applications.  From libpng 1.6.0 this function is also used
  351.  * internally to implement the png_info release part of the 'struct' destroy
  352.  * APIs.  This ensures that all possible approaches free the same data (all of
  353.  * it).
  354.  */
  355. void PNGAPI
  356. png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)
  357. {
  358.    png_inforp info_ptr = NULL;
  359.  
  360.    png_debug(1, "in png_destroy_info_struct");
  361.  
  362.    if (png_ptr == NULL)
  363.       return;
  364.  
  365.    if (info_ptr_ptr != NULL)
  366.       info_ptr = *info_ptr_ptr;
  367.  
  368.    if (info_ptr != NULL)
  369.    {
  370.       /* Do this first in case of an error below; if the app implements its own
  371.        * memory management this can lead to png_free calling png_error, which
  372.        * will abort this routine and return control to the app error handler.
  373.        * An infinite loop may result if it then tries to free the same info
  374.        * ptr.
  375.        */
  376.       *info_ptr_ptr = NULL;
  377.  
  378.       png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
  379.       memset(info_ptr, 0, (sizeof *info_ptr));
  380.       png_free(png_ptr, info_ptr);
  381.    }
  382. }
  383.  
  384. /* Initialize the info structure.  This is now an internal function (0.89)
  385.  * and applications using it are urged to use png_create_info_struct()
  386.  * instead.  Use deprecated in 1.6.0, internal use removed (used internally it
  387.  * is just a memset).
  388.  *
  389.  * NOTE: it is almost inconceivable that this API is used because it bypasses
  390.  * the user-memory mechanism and the user error handling/warning mechanisms in
  391.  * those cases where it does anything other than a memset.
  392.  */
  393. PNG_FUNCTION(void,PNGAPI
  394. png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),
  395.    PNG_DEPRECATED)
  396. {
  397.    png_inforp info_ptr = *ptr_ptr;
  398.  
  399.    png_debug(1, "in png_info_init_3");
  400.  
  401.    if (info_ptr == NULL)
  402.       return;
  403.  
  404.    if ((sizeof (png_info)) > png_info_struct_size)
  405.    {
  406.       *ptr_ptr = NULL;
  407.       /* The following line is why this API should not be used: */
  408.       free(info_ptr);
  409.       info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
  410.          (sizeof *info_ptr)));
  411.       *ptr_ptr = info_ptr;
  412.    }
  413.  
  414.    /* Set everything to 0 */
  415.    memset(info_ptr, 0, (sizeof *info_ptr));
  416. }
  417.  
  418. /* The following API is not called internally */
  419. void PNGAPI
  420. png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,
  421.    int freer, png_uint_32 mask)
  422. {
  423.    png_debug(1, "in png_data_freer");
  424.  
  425.    if (png_ptr == NULL || info_ptr == NULL)
  426.       return;
  427.  
  428.    if (freer == PNG_DESTROY_WILL_FREE_DATA)
  429.       info_ptr->free_me |= mask;
  430.  
  431.    else if (freer == PNG_USER_WILL_FREE_DATA)
  432.       info_ptr->free_me &= ~mask;
  433.  
  434.    else
  435.       png_error(png_ptr, "Unknown freer parameter in png_data_freer");
  436. }
  437.  
  438. void PNGAPI
  439. png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,
  440.    int num)
  441. {
  442.    png_debug(1, "in png_free_data");
  443.  
  444.    if (png_ptr == NULL || info_ptr == NULL)
  445.       return;
  446.  
  447. #ifdef PNG_TEXT_SUPPORTED
  448.    /* Free text item num or (if num == -1) all text items */
  449.    if ((mask & PNG_FREE_TEXT) & info_ptr->free_me)
  450.    {
  451.       if (num != -1)
  452.       {
  453.          if (info_ptr->text && info_ptr->text[num].key)
  454.          {
  455.             png_free(png_ptr, info_ptr->text[num].key);
  456.             info_ptr->text[num].key = NULL;
  457.          }
  458.       }
  459.  
  460.       else
  461.       {
  462.          int i;
  463.          for (i = 0; i < info_ptr->num_text; i++)
  464.              png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);
  465.          png_free(png_ptr, info_ptr->text);
  466.          info_ptr->text = NULL;
  467.          info_ptr->num_text=0;
  468.       }
  469.    }
  470. #endif
  471.  
  472. #ifdef PNG_tRNS_SUPPORTED
  473.    /* Free any tRNS entry */
  474.    if ((mask & PNG_FREE_TRNS) & info_ptr->free_me)
  475.    {
  476.       png_free(png_ptr, info_ptr->trans_alpha);
  477.       info_ptr->trans_alpha = NULL;
  478.       info_ptr->valid &= ~PNG_INFO_tRNS;
  479.    }
  480. #endif
  481.  
  482. #ifdef PNG_sCAL_SUPPORTED
  483.    /* Free any sCAL entry */
  484.    if ((mask & PNG_FREE_SCAL) & info_ptr->free_me)
  485.    {
  486.       png_free(png_ptr, info_ptr->scal_s_width);
  487.       png_free(png_ptr, info_ptr->scal_s_height);
  488.       info_ptr->scal_s_width = NULL;
  489.       info_ptr->scal_s_height = NULL;
  490.       info_ptr->valid &= ~PNG_INFO_sCAL;
  491.    }
  492. #endif
  493.  
  494. #ifdef PNG_pCAL_SUPPORTED
  495.    /* Free any pCAL entry */
  496.    if ((mask & PNG_FREE_PCAL) & info_ptr->free_me)
  497.    {
  498.       png_free(png_ptr, info_ptr->pcal_purpose);
  499.       png_free(png_ptr, info_ptr->pcal_units);
  500.       info_ptr->pcal_purpose = NULL;
  501.       info_ptr->pcal_units = NULL;
  502.       if (info_ptr->pcal_params != NULL)
  503.          {
  504.             unsigned int i;
  505.             for (i = 0; i < info_ptr->pcal_nparams; i++)
  506.             {
  507.                png_free(png_ptr, info_ptr->pcal_params[i]);
  508.                info_ptr->pcal_params[i] = NULL;
  509.             }
  510.             png_free(png_ptr, info_ptr->pcal_params);
  511.             info_ptr->pcal_params = NULL;
  512.          }
  513.       info_ptr->valid &= ~PNG_INFO_pCAL;
  514.    }
  515. #endif
  516.  
  517. #ifdef PNG_iCCP_SUPPORTED
  518.    /* Free any profile entry */
  519.    if ((mask & PNG_FREE_ICCP) & info_ptr->free_me)
  520.    {
  521.       png_free(png_ptr, info_ptr->iccp_name);
  522.       png_free(png_ptr, info_ptr->iccp_profile);
  523.       info_ptr->iccp_name = NULL;
  524.       info_ptr->iccp_profile = NULL;
  525.       info_ptr->valid &= ~PNG_INFO_iCCP;
  526.    }
  527. #endif
  528.  
  529. #ifdef PNG_sPLT_SUPPORTED
  530.    /* Free a given sPLT entry, or (if num == -1) all sPLT entries */
  531.    if ((mask & PNG_FREE_SPLT) & info_ptr->free_me)
  532.    {
  533.       if (num != -1)
  534.       {
  535.          if (info_ptr->splt_palettes)
  536.          {
  537.             png_free(png_ptr, info_ptr->splt_palettes[num].name);
  538.             png_free(png_ptr, info_ptr->splt_palettes[num].entries);
  539.             info_ptr->splt_palettes[num].name = NULL;
  540.             info_ptr->splt_palettes[num].entries = NULL;
  541.          }
  542.       }
  543.  
  544.       else
  545.       {
  546.          if (info_ptr->splt_palettes_num)
  547.          {
  548.             int i;
  549.             for (i = 0; i < info_ptr->splt_palettes_num; i++)
  550.                png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, (int)i);
  551.  
  552.             png_free(png_ptr, info_ptr->splt_palettes);
  553.             info_ptr->splt_palettes = NULL;
  554.             info_ptr->splt_palettes_num = 0;
  555.          }
  556.          info_ptr->valid &= ~PNG_INFO_sPLT;
  557.       }
  558.    }
  559. #endif
  560.  
  561. #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
  562.    if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)
  563.    {
  564.       if (num != -1)
  565.       {
  566.           if (info_ptr->unknown_chunks)
  567.           {
  568.              png_free(png_ptr, info_ptr->unknown_chunks[num].data);
  569.              info_ptr->unknown_chunks[num].data = NULL;
  570.           }
  571.       }
  572.  
  573.       else
  574.       {
  575.          int i;
  576.  
  577.          if (info_ptr->unknown_chunks_num)
  578.          {
  579.             for (i = 0; i < info_ptr->unknown_chunks_num; i++)
  580.                png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, (int)i);
  581.  
  582.             png_free(png_ptr, info_ptr->unknown_chunks);
  583.             info_ptr->unknown_chunks = NULL;
  584.             info_ptr->unknown_chunks_num = 0;
  585.          }
  586.       }
  587.    }
  588. #endif
  589.  
  590. #ifdef PNG_hIST_SUPPORTED
  591.    /* Free any hIST entry */
  592.    if ((mask & PNG_FREE_HIST)  & info_ptr->free_me)
  593.    {
  594.       png_free(png_ptr, info_ptr->hist);
  595.       info_ptr->hist = NULL;
  596.       info_ptr->valid &= ~PNG_INFO_hIST;
  597.    }
  598. #endif
  599.  
  600.    /* Free any PLTE entry that was internally allocated */
  601.    if ((mask & PNG_FREE_PLTE) & info_ptr->free_me)
  602.    {
  603.       png_free(png_ptr, info_ptr->palette);
  604.       info_ptr->palette = NULL;
  605.       info_ptr->valid &= ~PNG_INFO_PLTE;
  606.       info_ptr->num_palette = 0;
  607.    }
  608.  
  609. #ifdef PNG_INFO_IMAGE_SUPPORTED
  610.    /* Free any image bits attached to the info structure */
  611.    if ((mask & PNG_FREE_ROWS) & info_ptr->free_me)
  612.    {
  613.       if (info_ptr->row_pointers)
  614.       {
  615.          png_uint_32 row;
  616.          for (row = 0; row < info_ptr->height; row++)
  617.          {
  618.             png_free(png_ptr, info_ptr->row_pointers[row]);
  619.             info_ptr->row_pointers[row] = NULL;
  620.          }
  621.          png_free(png_ptr, info_ptr->row_pointers);
  622.          info_ptr->row_pointers = NULL;
  623.       }
  624.       info_ptr->valid &= ~PNG_INFO_IDAT;
  625.    }
  626. #endif
  627.  
  628.    if (num != -1)
  629.       mask &= ~PNG_FREE_MUL;
  630.  
  631.    info_ptr->free_me &= ~mask;
  632. }
  633. #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
  634.  
  635. /* This function returns a pointer to the io_ptr associated with the user
  636.  * functions.  The application should free any memory associated with this
  637.  * pointer before png_write_destroy() or png_read_destroy() are called.
  638.  */
  639. png_voidp PNGAPI
  640. png_get_io_ptr(png_const_structrp png_ptr)
  641. {
  642.    if (png_ptr == NULL)
  643.       return (NULL);
  644.  
  645.    return (png_ptr->io_ptr);
  646. }
  647.  
  648. #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  649. #  ifdef PNG_STDIO_SUPPORTED
  650. /* Initialize the default input/output functions for the PNG file.  If you
  651.  * use your own read or write routines, you can call either png_set_read_fn()
  652.  * or png_set_write_fn() instead of png_init_io().  If you have defined
  653.  * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
  654.  * function of your own because "FILE *" isn't necessarily available.
  655.  */
  656. void PNGAPI
  657. png_init_io(png_structrp png_ptr, png_FILE_p fp)
  658. {
  659.    png_debug(1, "in png_init_io");
  660.  
  661.    if (png_ptr == NULL)
  662.       return;
  663.  
  664.    png_ptr->io_ptr = (png_voidp)fp;
  665. }
  666. #  endif
  667.  
  668. #ifdef PNG_SAVE_INT_32_SUPPORTED
  669. /* The png_save_int_32 function assumes integers are stored in two's
  670.  * complement format.  If this isn't the case, then this routine needs to
  671.  * be modified to write data in two's complement format.  Note that,
  672.  * the following works correctly even if png_int_32 has more than 32 bits
  673.  * (compare the more complex code required on read for sign extension.)
  674.  */
  675. void PNGAPI
  676. png_save_int_32(png_bytep buf, png_int_32 i)
  677. {
  678.    buf[0] = (png_byte)((i >> 24) & 0xff);
  679.    buf[1] = (png_byte)((i >> 16) & 0xff);
  680.    buf[2] = (png_byte)((i >> 8) & 0xff);
  681.    buf[3] = (png_byte)(i & 0xff);
  682. }
  683. #endif
  684.  
  685. #  ifdef PNG_TIME_RFC1123_SUPPORTED
  686. /* Convert the supplied time into an RFC 1123 string suitable for use in
  687.  * a "Creation Time" or other text-based time string.
  688.  */
  689. int PNGAPI
  690. png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
  691. {
  692.    static PNG_CONST char short_months[12][4] =
  693.         {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
  694.          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
  695.  
  696.    if (out == NULL)
  697.       return 0;
  698.  
  699.    if (ptime->year > 9999 /* RFC1123 limitation */ ||
  700.        ptime->month == 0    ||  ptime->month > 12  ||
  701.        ptime->day   == 0    ||  ptime->day   > 31  ||
  702.        ptime->hour  > 23    ||  ptime->minute > 59 ||
  703.        ptime->second > 60)
  704.       return 0;
  705.  
  706.    {
  707.       size_t pos = 0;
  708.       char number_buf[5]; /* enough for a four-digit year */
  709.  
  710. #     define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))
  711. #     define APPEND_NUMBER(format, value)\
  712.          APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
  713. #     define APPEND(ch) if (pos < 28) out[pos++] = (ch)
  714.  
  715.       APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day);
  716.       APPEND(' ');
  717.       APPEND_STRING(short_months[(ptime->month - 1)]);
  718.       APPEND(' ');
  719.       APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);
  720.       APPEND(' ');
  721.       APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour);
  722.       APPEND(':');
  723.       APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute);
  724.       APPEND(':');
  725.       APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);
  726.       APPEND_STRING(" +0000"); /* This reliably terminates the buffer */
  727.  
  728. #     undef APPEND
  729. #     undef APPEND_NUMBER
  730. #     undef APPEND_STRING
  731.    }
  732.  
  733.    return 1;
  734. }
  735.  
  736. #     if PNG_LIBPNG_VER < 10700
  737. /* To do: remove the following from libpng-1.7 */
  738. /* Original API that uses a private buffer in png_struct.
  739.  * Deprecated because it causes png_struct to carry a spurious temporary
  740.  * buffer (png_struct::time_buffer), better to have the caller pass this in.
  741.  */
  742. png_const_charp PNGAPI
  743. png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)
  744. {
  745.    if (png_ptr != NULL)
  746.    {
  747.       /* The only failure above if png_ptr != NULL is from an invalid ptime */
  748.       if (!png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime))
  749.          png_warning(png_ptr, "Ignoring invalid time value");
  750.  
  751.       else
  752.          return png_ptr->time_buffer;
  753.    }
  754.  
  755.    return NULL;
  756. }
  757. #     endif
  758. #  endif /* PNG_TIME_RFC1123_SUPPORTED */
  759.  
  760. #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
  761.  
  762. png_const_charp PNGAPI
  763. png_get_copyright(png_const_structrp png_ptr)
  764. {
  765.    PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
  766. #ifdef PNG_STRING_COPYRIGHT
  767.    return PNG_STRING_COPYRIGHT
  768. #else
  769. #  ifdef __STDC__
  770.    return PNG_STRING_NEWLINE \
  771.      "libpng version 1.6.5 - September 14, 2013" PNG_STRING_NEWLINE \
  772.      "Copyright (c) 1998-2013 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
  773.      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
  774.      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
  775.      PNG_STRING_NEWLINE;
  776. #  else
  777.       return "libpng version 1.6.5 - September 14, 2013\
  778.      Copyright (c) 1998-2013 Glenn Randers-Pehrson\
  779.      Copyright (c) 1996-1997 Andreas Dilger\
  780.      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
  781. #  endif
  782. #endif
  783. }
  784.  
  785. /* The following return the library version as a short string in the
  786.  * format 1.0.0 through 99.99.99zz.  To get the version of *.h files
  787.  * used with your application, print out PNG_LIBPNG_VER_STRING, which
  788.  * is defined in png.h.
  789.  * Note: now there is no difference between png_get_libpng_ver() and
  790.  * png_get_header_ver().  Due to the version_nn_nn_nn typedef guard,
  791.  * it is guaranteed that png.c uses the correct version of png.h.
  792.  */
  793. png_const_charp PNGAPI
  794. png_get_libpng_ver(png_const_structrp png_ptr)
  795. {
  796.    /* Version of *.c files used when building libpng */
  797.    return png_get_header_ver(png_ptr);
  798. }
  799.  
  800. png_const_charp PNGAPI
  801. png_get_header_ver(png_const_structrp png_ptr)
  802. {
  803.    /* Version of *.h files used when building libpng */
  804.    PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
  805.    return PNG_LIBPNG_VER_STRING;
  806. }
  807.  
  808. png_const_charp PNGAPI
  809. png_get_header_version(png_const_structrp png_ptr)
  810. {
  811.    /* Returns longer string containing both version and date */
  812.    PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */
  813. #ifdef __STDC__
  814.    return PNG_HEADER_VERSION_STRING
  815. #  ifndef PNG_READ_SUPPORTED
  816.    "     (NO READ SUPPORT)"
  817. #  endif
  818.    PNG_STRING_NEWLINE;
  819. #else
  820.    return PNG_HEADER_VERSION_STRING;
  821. #endif
  822. }
  823.  
  824. #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
  825. int PNGAPI
  826. png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)
  827. {
  828.    /* Check chunk_name and return "keep" value if it's on the list, else 0 */
  829.    png_const_bytep p, p_end;
  830.  
  831.    if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0)
  832.       return PNG_HANDLE_CHUNK_AS_DEFAULT;
  833.  
  834.    p_end = png_ptr->chunk_list;
  835.    p = p_end + png_ptr->num_chunk_list*5; /* beyond end */
  836.  
  837.    /* The code is the fifth byte after each four byte string.  Historically this
  838.     * code was always searched from the end of the list, this is no longer
  839.     * necessary because the 'set' routine handles duplicate entries correcty.
  840.     */
  841.    do /* num_chunk_list > 0, so at least one */
  842.    {
  843.       p -= 5;
  844.  
  845.       if (!memcmp(chunk_name, p, 4))
  846.          return p[4];
  847.    }
  848.    while (p > p_end);
  849.  
  850.    /* This means that known chunks should be processed and unknown chunks should
  851.     * be handled according to the value of png_ptr->unknown_default; this can be
  852.     * confusing because, as a result, there are two levels of defaulting for
  853.     * unknown chunks.
  854.     */
  855.    return PNG_HANDLE_CHUNK_AS_DEFAULT;
  856. }
  857.  
  858. #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
  859. int /* PRIVATE */
  860. png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)
  861. {
  862.    png_byte chunk_string[5];
  863.  
  864.    PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);
  865.    return png_handle_as_unknown(png_ptr, chunk_string);
  866. }
  867. #endif /* HANDLE_AS_UNKNOWN */
  868. #endif /* SET_UNKNOWN_CHUNKS */
  869.  
  870. #ifdef PNG_READ_SUPPORTED
  871. /* This function, added to libpng-1.0.6g, is untested. */
  872. int PNGAPI
  873. png_reset_zstream(png_structrp png_ptr)
  874. {
  875.    if (png_ptr == NULL)
  876.       return Z_STREAM_ERROR;
  877.  
  878.    /* WARNING: this resets the window bits to the maximum! */
  879.    return (inflateReset(&png_ptr->zstream));
  880. }
  881. #endif /* PNG_READ_SUPPORTED */
  882.  
  883. /* This function was added to libpng-1.0.7 */
  884. png_uint_32 PNGAPI
  885. png_access_version_number(void)
  886. {
  887.    /* Version of *.c files used when building libpng */
  888.    return((png_uint_32)PNG_LIBPNG_VER);
  889. }
  890.  
  891.  
  892.  
  893. #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  894. /* Ensure that png_ptr->zstream.msg holds some appropriate error message string.
  895.  * If it doesn't 'ret' is used to set it to something appropriate, even in cases
  896.  * like Z_OK or Z_STREAM_END where the error code is apparently a success code.
  897.  */
  898. void /* PRIVATE */
  899. png_zstream_error(png_structrp png_ptr, int ret)
  900. {
  901.    /* Translate 'ret' into an appropriate error string, priority is given to the
  902.     * one in zstream if set.  This always returns a string, even in cases like
  903.     * Z_OK or Z_STREAM_END where the error code is a success code.
  904.     */
  905.    if (png_ptr->zstream.msg == NULL) switch (ret)
  906.    {
  907.       default:
  908.       case Z_OK:
  909.          png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code");
  910.          break;
  911.  
  912.       case Z_STREAM_END:
  913.          /* Normal exit */
  914.          png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream");
  915.          break;
  916.  
  917.       case Z_NEED_DICT:
  918.          /* This means the deflate stream did not have a dictionary; this
  919.           * indicates a bogus PNG.
  920.           */
  921.          png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary");
  922.          break;
  923.  
  924.       case Z_ERRNO:
  925.          /* gz APIs only: should not happen */
  926.          png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error");
  927.          break;
  928.  
  929.       case Z_STREAM_ERROR:
  930.          /* internal libpng error */
  931.          png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib");
  932.          break;
  933.  
  934.       case Z_DATA_ERROR:
  935.          png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream");
  936.          break;
  937.  
  938.       case Z_MEM_ERROR:
  939.          png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory");
  940.          break;
  941.  
  942.       case Z_BUF_ERROR:
  943.          /* End of input or output; not a problem if the caller is doing
  944.           * incremental read or write.
  945.           */
  946.          png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated");
  947.          break;
  948.  
  949.       case Z_VERSION_ERROR:
  950.          png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version");
  951.          break;
  952.  
  953.       case PNG_UNEXPECTED_ZLIB_RETURN:
  954.          /* Compile errors here mean that zlib now uses the value co-opted in
  955.           * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above
  956.           * and change pngpriv.h.  Note that this message is "... return",
  957.           * whereas the default/Z_OK one is "... return code".
  958.           */
  959.          png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return");
  960.          break;
  961.    }
  962. }
  963.  
  964. /* png_convert_size: a PNGAPI but no longer in png.h, so deleted
  965.  * at libpng 1.5.5!
  966.  */
  967.  
  968. /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
  969. #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */
  970. static int
  971. png_colorspace_check_gamma(png_const_structrp png_ptr,
  972.    png_colorspacerp colorspace, png_fixed_point gAMA, int from)
  973.    /* This is called to check a new gamma value against an existing one.  The
  974.     * routine returns false if the new gamma value should not be written.
  975.     *
  976.     * 'from' says where the new gamma value comes from:
  977.     *
  978.     *    0: the new gamma value is the libpng estimate for an ICC profile
  979.     *    1: the new gamma value comes from a gAMA chunk
  980.     *    2: the new gamma value comes from an sRGB chunk
  981.     */
  982. {
  983.    png_fixed_point gtest;
  984.  
  985.    if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
  986.       (!png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) ||
  987.       png_gamma_significant(gtest)))
  988.    {
  989.       /* Either this is an sRGB image, in which case the calculated gamma
  990.        * approximation should match, or this is an image with a profile and the
  991.        * value libpng calculates for the gamma of the profile does not match the
  992.        * value recorded in the file.  The former, sRGB, case is an error, the
  993.        * latter is just a warning.
  994.        */
  995.       if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)
  996.       {
  997.          png_chunk_report(png_ptr, "gamma value does not match sRGB",
  998.             PNG_CHUNK_ERROR);
  999.          /* Do not overwrite an sRGB value */
  1000.          return from == 2;
  1001.       }
  1002.  
  1003.       else /* sRGB tag not involved */
  1004.       {
  1005.          png_chunk_report(png_ptr, "gamma value does not match libpng estimate",
  1006.             PNG_CHUNK_WARNING);
  1007.          return from == 1;
  1008.       }
  1009.    }
  1010.  
  1011.    return 1;
  1012. }
  1013.  
  1014. void /* PRIVATE */
  1015. png_colorspace_set_gamma(png_const_structrp png_ptr,
  1016.    png_colorspacerp colorspace, png_fixed_point gAMA)
  1017. {
  1018.    /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
  1019.     * occur.  Since the fixed point representation is assymetrical it is
  1020.     * possible for 1/gamma to overflow the limit of 21474 and this means the
  1021.     * gamma value must be at least 5/100000 and hence at most 20000.0.  For
  1022.     * safety the limits here are a little narrower.  The values are 0.00016 to
  1023.     * 6250.0, which are truly ridiculous gamma values (and will produce
  1024.     * displays that are all black or all white.)
  1025.     *
  1026.     * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk
  1027.     * handling code, which only required the value to be >0.
  1028.     */
  1029.    png_const_charp errmsg;
  1030.  
  1031.    if (gAMA < 16 || gAMA > 625000000)
  1032.       errmsg = "gamma value out of range";
  1033.  
  1034. #  ifdef PNG_READ_gAMA_SUPPORTED
  1035.       /* Allow the application to set the gamma value more than once */
  1036.       else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
  1037.          (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
  1038.          errmsg = "duplicate";
  1039. #  endif
  1040.  
  1041.    /* Do nothing if the colorspace is already invalid */
  1042.    else if (colorspace->flags & PNG_COLORSPACE_INVALID)
  1043.       return;
  1044.  
  1045.    else
  1046.    {
  1047.       if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA, 1/*from gAMA*/))
  1048.       {
  1049.          /* Store this gamma value. */
  1050.          colorspace->gamma = gAMA;
  1051.          colorspace->flags |=
  1052.             (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA);
  1053.       }
  1054.  
  1055.       /* At present if the check_gamma test fails the gamma of the colorspace is
  1056.        * not updated however the colorspace is not invalidated.  This
  1057.        * corresponds to the case where the existing gamma comes from an sRGB
  1058.        * chunk or profile.  An error message has already been output.
  1059.        */
  1060.       return;
  1061.    }
  1062.  
  1063.    /* Error exit - errmsg has been set. */
  1064.    colorspace->flags |= PNG_COLORSPACE_INVALID;
  1065.    png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR);
  1066. }
  1067.  
  1068. void /* PRIVATE */
  1069. png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)
  1070. {
  1071.    if (info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
  1072.    {
  1073.       /* Everything is invalid */
  1074.       info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB|
  1075.          PNG_INFO_iCCP);
  1076.  
  1077. #     ifdef PNG_COLORSPACE_SUPPORTED
  1078.          /* Clean up the iCCP profile now if it won't be used. */
  1079.          png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
  1080. #     else
  1081.          PNG_UNUSED(png_ptr)
  1082. #     endif
  1083.    }
  1084.  
  1085.    else
  1086.    {
  1087. #     ifdef PNG_COLORSPACE_SUPPORTED
  1088.          /* Leave the INFO_iCCP flag set if the pngset.c code has already set
  1089.           * it; this allows a PNG to contain a profile which matches sRGB and
  1090.           * yet still have that profile retrievable by the application.
  1091.           */
  1092.          if (info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB)
  1093.             info_ptr->valid |= PNG_INFO_sRGB;
  1094.  
  1095.          else
  1096.             info_ptr->valid &= ~PNG_INFO_sRGB;
  1097.  
  1098.          if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS)
  1099.             info_ptr->valid |= PNG_INFO_cHRM;
  1100.  
  1101.          else
  1102.             info_ptr->valid &= ~PNG_INFO_cHRM;
  1103. #     endif
  1104.  
  1105.       if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA)
  1106.          info_ptr->valid |= PNG_INFO_gAMA;
  1107.  
  1108.       else
  1109.          info_ptr->valid &= ~PNG_INFO_gAMA;
  1110.    }
  1111. }
  1112.  
  1113. #ifdef PNG_READ_SUPPORTED
  1114. void /* PRIVATE */
  1115. png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)
  1116. {
  1117.    if (info_ptr == NULL) /* reduce code size; check here not in the caller */
  1118.       return;
  1119.  
  1120.    info_ptr->colorspace = png_ptr->colorspace;
  1121.    png_colorspace_sync_info(png_ptr, info_ptr);
  1122. }
  1123. #endif
  1124. #endif
  1125.  
  1126. #ifdef PNG_COLORSPACE_SUPPORTED
  1127. /* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
  1128.  * cHRM, as opposed to using chromaticities.  These internal APIs return
  1129.  * non-zero on a parameter error.  The X, Y and Z values are required to be
  1130.  * positive and less than 1.0.
  1131.  */
  1132. static int
  1133. png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)
  1134. {
  1135.    png_int_32 d, dwhite, whiteX, whiteY;
  1136.  
  1137.    d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;
  1138.    if (!png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d)) return 1;
  1139.    if (!png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d)) return 1;
  1140.    dwhite = d;
  1141.    whiteX = XYZ->red_X;
  1142.    whiteY = XYZ->red_Y;
  1143.  
  1144.    d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;
  1145.    if (!png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d)) return 1;
  1146.    if (!png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d)) return 1;
  1147.    dwhite += d;
  1148.    whiteX += XYZ->green_X;
  1149.    whiteY += XYZ->green_Y;
  1150.  
  1151.    d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;
  1152.    if (!png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d)) return 1;
  1153.    if (!png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d)) return 1;
  1154.    dwhite += d;
  1155.    whiteX += XYZ->blue_X;
  1156.    whiteY += XYZ->blue_Y;
  1157.  
  1158.    /* The reference white is simply the sum of the end-point (X,Y,Z) vectors,
  1159.     * thus:
  1160.     */
  1161.    if (!png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite)) return 1;
  1162.    if (!png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite)) return 1;
  1163.  
  1164.    return 0;
  1165. }
  1166.  
  1167. static int
  1168. png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)
  1169. {
  1170.    png_fixed_point red_inverse, green_inverse, blue_scale;
  1171.    png_fixed_point left, right, denominator;
  1172.  
  1173.    /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically
  1174.     * have end points with 0 tristimulus values (these are impossible end
  1175.     * points, but they are used to cover the possible colors.)
  1176.     */
  1177.    if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1;
  1178.    if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
  1179.    if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;
  1180.    if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;
  1181.    if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1;
  1182.    if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
  1183.    if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;
  1184.    if (xy->whitey < 0 || xy->whitey > PNG_FP_1-xy->whitex) return 1;
  1185.  
  1186.    /* The reverse calculation is more difficult because the original tristimulus
  1187.     * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
  1188.     * derived values were recorded in the cHRM chunk;
  1189.     * (red,green,blue,white)x(x,y).  This loses one degree of freedom and
  1190.     * therefore an arbitrary ninth value has to be introduced to undo the
  1191.     * original transformations.
  1192.     *
  1193.     * Think of the original end-points as points in (X,Y,Z) space.  The
  1194.     * chromaticity values (c) have the property:
  1195.     *
  1196.     *           C
  1197.     *   c = ---------
  1198.     *       X + Y + Z
  1199.     *
  1200.     * For each c (x,y,z) from the corresponding original C (X,Y,Z).  Thus the
  1201.     * three chromaticity values (x,y,z) for each end-point obey the
  1202.     * relationship:
  1203.     *
  1204.     *   x + y + z = 1
  1205.     *
  1206.     * This describes the plane in (X,Y,Z) space that intersects each axis at the
  1207.     * value 1.0; call this the chromaticity plane.  Thus the chromaticity
  1208.     * calculation has scaled each end-point so that it is on the x+y+z=1 plane
  1209.     * and chromaticity is the intersection of the vector from the origin to the
  1210.     * (X,Y,Z) value with the chromaticity plane.
  1211.     *
  1212.     * To fully invert the chromaticity calculation we would need the three
  1213.     * end-point scale factors, (red-scale, green-scale, blue-scale), but these
  1214.     * were not recorded.  Instead we calculated the reference white (X,Y,Z) and
  1215.     * recorded the chromaticity of this.  The reference white (X,Y,Z) would have
  1216.     * given all three of the scale factors since:
  1217.     *
  1218.     *    color-C = color-c * color-scale
  1219.     *    white-C = red-C + green-C + blue-C
  1220.     *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
  1221.     *
  1222.     * But cHRM records only white-x and white-y, so we have lost the white scale
  1223.     * factor:
  1224.     *
  1225.     *    white-C = white-c*white-scale
  1226.     *
  1227.     * To handle this the inverse transformation makes an arbitrary assumption
  1228.     * about white-scale:
  1229.     *
  1230.     *    Assume: white-Y = 1.0
  1231.     *    Hence:  white-scale = 1/white-y
  1232.     *    Or:     red-Y + green-Y + blue-Y = 1.0
  1233.     *
  1234.     * Notice the last statement of the assumption gives an equation in three of
  1235.     * the nine values we want to calculate.  8 more equations come from the
  1236.     * above routine as summarised at the top above (the chromaticity
  1237.     * calculation):
  1238.     *
  1239.     *    Given: color-x = color-X / (color-X + color-Y + color-Z)
  1240.     *    Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0
  1241.     *
  1242.     * This is 9 simultaneous equations in the 9 variables "color-C" and can be
  1243.     * solved by Cramer's rule.  Cramer's rule requires calculating 10 9x9 matrix
  1244.     * determinants, however this is not as bad as it seems because only 28 of
  1245.     * the total of 90 terms in the various matrices are non-zero.  Nevertheless
  1246.     * Cramer's rule is notoriously numerically unstable because the determinant
  1247.     * calculation involves the difference of large, but similar, numbers.  It is
  1248.     * difficult to be sure that the calculation is stable for real world values
  1249.     * and it is certain that it becomes unstable where the end points are close
  1250.     * together.
  1251.     *
  1252.     * So this code uses the perhaps slightly less optimal but more
  1253.     * understandable and totally obvious approach of calculating color-scale.
  1254.     *
  1255.     * This algorithm depends on the precision in white-scale and that is
  1256.     * (1/white-y), so we can immediately see that as white-y approaches 0 the
  1257.     * accuracy inherent in the cHRM chunk drops off substantially.
  1258.     *
  1259.     * libpng arithmetic: a simple invertion of the above equations
  1260.     * ------------------------------------------------------------
  1261.     *
  1262.     *    white_scale = 1/white-y
  1263.     *    white-X = white-x * white-scale
  1264.     *    white-Y = 1.0
  1265.     *    white-Z = (1 - white-x - white-y) * white_scale
  1266.     *
  1267.     *    white-C = red-C + green-C + blue-C
  1268.     *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
  1269.     *
  1270.     * This gives us three equations in (red-scale,green-scale,blue-scale) where
  1271.     * all the coefficients are now known:
  1272.     *
  1273.     *    red-x*red-scale + green-x*green-scale + blue-x*blue-scale
  1274.     *       = white-x/white-y
  1275.     *    red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
  1276.     *    red-z*red-scale + green-z*green-scale + blue-z*blue-scale
  1277.     *       = (1 - white-x - white-y)/white-y
  1278.     *
  1279.     * In the last equation color-z is (1 - color-x - color-y) so we can add all
  1280.     * three equations together to get an alternative third:
  1281.     *
  1282.     *    red-scale + green-scale + blue-scale = 1/white-y = white-scale
  1283.     *
  1284.     * So now we have a Cramer's rule solution where the determinants are just
  1285.     * 3x3 - far more tractible.  Unfortunately 3x3 determinants still involve
  1286.     * multiplication of three coefficients so we can't guarantee to avoid
  1287.     * overflow in the libpng fixed point representation.  Using Cramer's rule in
  1288.     * floating point is probably a good choice here, but it's not an option for
  1289.     * fixed point.  Instead proceed to simplify the first two equations by
  1290.     * eliminating what is likely to be the largest value, blue-scale:
  1291.     *
  1292.     *    blue-scale = white-scale - red-scale - green-scale
  1293.     *
  1294.     * Hence:
  1295.     *
  1296.     *    (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =
  1297.     *                (white-x - blue-x)*white-scale
  1298.     *
  1299.     *    (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =
  1300.     *                1 - blue-y*white-scale
  1301.     *
  1302.     * And now we can trivially solve for (red-scale,green-scale):
  1303.     *
  1304.     *    green-scale =
  1305.     *                (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale
  1306.     *                -----------------------------------------------------------
  1307.     *                                  green-x - blue-x
  1308.     *
  1309.     *    red-scale =
  1310.     *                1 - blue-y*white-scale - (green-y - blue-y) * green-scale
  1311.     *                ---------------------------------------------------------
  1312.     *                                  red-y - blue-y
  1313.     *
  1314.     * Hence:
  1315.     *
  1316.     *    red-scale =
  1317.     *          ( (green-x - blue-x) * (white-y - blue-y) -
  1318.     *            (green-y - blue-y) * (white-x - blue-x) ) / white-y
  1319.     * -------------------------------------------------------------------------
  1320.     *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
  1321.     *
  1322.     *    green-scale =
  1323.     *          ( (red-y - blue-y) * (white-x - blue-x) -
  1324.     *            (red-x - blue-x) * (white-y - blue-y) ) / white-y
  1325.     * -------------------------------------------------------------------------
  1326.     *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
  1327.     *
  1328.     * Accuracy:
  1329.     * The input values have 5 decimal digits of accuracy.  The values are all in
  1330.     * the range 0 < value < 1, so simple products are in the same range but may
  1331.     * need up to 10 decimal digits to preserve the original precision and avoid
  1332.     * underflow.  Because we are using a 32-bit signed representation we cannot
  1333.     * match this; the best is a little over 9 decimal digits, less than 10.
  1334.     *
  1335.     * The approach used here is to preserve the maximum precision within the
  1336.     * signed representation.  Because the red-scale calculation above uses the
  1337.     * difference between two products of values that must be in the range -1..+1
  1338.     * it is sufficient to divide the product by 7; ceil(100,000/32767*2).  The
  1339.     * factor is irrelevant in the calculation because it is applied to both
  1340.     * numerator and denominator.
  1341.     *
  1342.     * Note that the values of the differences of the products of the
  1343.     * chromaticities in the above equations tend to be small, for example for
  1344.     * the sRGB chromaticities they are:
  1345.     *
  1346.     * red numerator:    -0.04751
  1347.     * green numerator:  -0.08788
  1348.     * denominator:      -0.2241 (without white-y multiplication)
  1349.     *
  1350.     *  The resultant Y coefficients from the chromaticities of some widely used
  1351.     *  color space definitions are (to 15 decimal places):
  1352.     *
  1353.     *  sRGB
  1354.     *    0.212639005871510 0.715168678767756 0.072192315360734
  1355.     *  Kodak ProPhoto
  1356.     *    0.288071128229293 0.711843217810102 0.000085653960605
  1357.     *  Adobe RGB
  1358.     *    0.297344975250536 0.627363566255466 0.075291458493998
  1359.     *  Adobe Wide Gamut RGB
  1360.     *    0.258728243040113 0.724682314948566 0.016589442011321
  1361.     */
  1362.    /* By the argument, above overflow should be impossible here. The return
  1363.     * value of 2 indicates an internal error to the caller.
  1364.     */
  1365.    if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7))
  1366.       return 2;
  1367.    if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7))
  1368.       return 2;
  1369.    denominator = left - right;
  1370.  
  1371.    /* Now find the red numerator. */
  1372.    if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7))
  1373.       return 2;
  1374.    if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7))
  1375.       return 2;
  1376.  
  1377.    /* Overflow is possible here and it indicates an extreme set of PNG cHRM
  1378.     * chunk values.  This calculation actually returns the reciprocal of the
  1379.     * scale value because this allows us to delay the multiplication of white-y
  1380.     * into the denominator, which tends to produce a small number.
  1381.     */
  1382.    if (!png_muldiv(&red_inverse, xy->whitey, denominator, left-right) ||
  1383.        red_inverse <= xy->whitey /* r+g+b scales = white scale */)
  1384.       return 1;
  1385.  
  1386.    /* Similarly for green_inverse: */
  1387.    if (!png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7))
  1388.       return 2;
  1389.    if (!png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7))
  1390.       return 2;
  1391.    if (!png_muldiv(&green_inverse, xy->whitey, denominator, left-right) ||
  1392.        green_inverse <= xy->whitey)
  1393.       return 1;
  1394.  
  1395.    /* And the blue scale, the checks above guarantee this can't overflow but it
  1396.     * can still produce 0 for extreme cHRM values.
  1397.     */
  1398.    blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) -
  1399.       png_reciprocal(green_inverse);
  1400.    if (blue_scale <= 0) return 1;
  1401.  
  1402.  
  1403.    /* And fill in the png_XYZ: */
  1404.    if (!png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse)) return 1;
  1405.    if (!png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse)) return 1;
  1406.    if (!png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
  1407.       red_inverse))
  1408.       return 1;
  1409.  
  1410.    if (!png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse))
  1411.       return 1;
  1412.    if (!png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse))
  1413.       return 1;
  1414.    if (!png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
  1415.       green_inverse))
  1416.       return 1;
  1417.  
  1418.    if (!png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1)) return 1;
  1419.    if (!png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1)) return 1;
  1420.    if (!png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
  1421.       PNG_FP_1))
  1422.       return 1;
  1423.  
  1424.    return 0; /*success*/
  1425. }
  1426.  
  1427. static int
  1428. png_XYZ_normalize(png_XYZ *XYZ)
  1429. {
  1430.    png_int_32 Y;
  1431.  
  1432.    if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||
  1433.       XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||
  1434.       XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)
  1435.       return 1;
  1436.  
  1437.    /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.
  1438.     * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
  1439.     * relying on addition of two positive values producing a negative one is not
  1440.     * safe.
  1441.     */
  1442.    Y = XYZ->red_Y;
  1443.    if (0x7fffffff - Y < XYZ->green_X) return 1;
  1444.    Y += XYZ->green_Y;
  1445.    if (0x7fffffff - Y < XYZ->blue_X) return 1;
  1446.    Y += XYZ->blue_Y;
  1447.  
  1448.    if (Y != PNG_FP_1)
  1449.    {
  1450.       if (!png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y)) return 1;
  1451.       if (!png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y)) return 1;
  1452.       if (!png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y)) return 1;
  1453.  
  1454.       if (!png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y)) return 1;
  1455.       if (!png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y)) return 1;
  1456.       if (!png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y)) return 1;
  1457.  
  1458.       if (!png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y)) return 1;
  1459.       if (!png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y)) return 1;
  1460.       if (!png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y)) return 1;
  1461.    }
  1462.  
  1463.    return 0;
  1464. }
  1465.  
  1466. static int
  1467. png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta)
  1468. {
  1469.    /* Allow an error of +/-0.01 (absolute value) on each chromaticity */
  1470.    return !(PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) ||
  1471.       PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) ||
  1472.       PNG_OUT_OF_RANGE(xy1->redx,   xy2->redx,  delta) ||
  1473.       PNG_OUT_OF_RANGE(xy1->redy,   xy2->redy,  delta) ||
  1474.       PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) ||
  1475.       PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) ||
  1476.       PNG_OUT_OF_RANGE(xy1->bluex,  xy2->bluex, delta) ||
  1477.       PNG_OUT_OF_RANGE(xy1->bluey,  xy2->bluey, delta));
  1478. }
  1479.  
  1480. /* Added in libpng-1.6.0, a different check for the validity of a set of cHRM
  1481.  * chunk chromaticities.  Earlier checks used to simply look for the overflow
  1482.  * condition (where the determinant of the matrix to solve for XYZ ends up zero
  1483.  * because the chromaticity values are not all distinct.)  Despite this it is
  1484.  * theoretically possible to produce chromaticities that are apparently valid
  1485.  * but that rapidly degrade to invalid, potentially crashing, sets because of
  1486.  * arithmetic inaccuracies when calculations are performed on them.  The new
  1487.  * check is to round-trip xy -> XYZ -> xy and then check that the result is
  1488.  * within a small percentage of the original.
  1489.  */
  1490. static int
  1491. png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy)
  1492. {
  1493.    int result;
  1494.    png_xy xy_test;
  1495.  
  1496.    /* As a side-effect this routine also returns the XYZ endpoints. */
  1497.    result = png_XYZ_from_xy(XYZ, xy);
  1498.    if (result) return result;
  1499.  
  1500.    result = png_xy_from_XYZ(&xy_test, XYZ);
  1501.    if (result) return result;
  1502.  
  1503.    if (png_colorspace_endpoints_match(xy, &xy_test,
  1504.       5/*actually, the math is pretty accurate*/))
  1505.       return 0;
  1506.  
  1507.    /* Too much slip */
  1508.    return 1;
  1509. }
  1510.  
  1511. /* This is the check going the other way.  The XYZ is modified to normalize it
  1512.  * (another side-effect) and the xy chromaticities are returned.
  1513.  */
  1514. static int
  1515. png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ)
  1516. {
  1517.    int result;
  1518.    png_XYZ XYZtemp;
  1519.  
  1520.    result = png_XYZ_normalize(XYZ);
  1521.    if (result) return result;
  1522.  
  1523.    result = png_xy_from_XYZ(xy, XYZ);
  1524.    if (result) return result;
  1525.  
  1526.    XYZtemp = *XYZ;
  1527.    return png_colorspace_check_xy(&XYZtemp, xy);
  1528. }
  1529.  
  1530. /* Used to check for an endpoint match against sRGB */
  1531. static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */
  1532. {
  1533.    /* color      x       y */
  1534.    /* red   */ 64000, 33000,
  1535.    /* green */ 30000, 60000,
  1536.    /* blue  */ 15000,  6000,
  1537.    /* white */ 31270, 32900
  1538. };
  1539.  
  1540. static int
  1541. png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,
  1542.    png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,
  1543.    int preferred)
  1544. {
  1545.    if (colorspace->flags & PNG_COLORSPACE_INVALID)
  1546.       return 0;
  1547.  
  1548.    /* The consistency check is performed on the chromaticities; this factors out
  1549.     * variations because of the normalization (or not) of the end point Y
  1550.     * values.
  1551.     */
  1552.    if (preferred < 2 && (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS))
  1553.    {
  1554.       /* The end points must be reasonably close to any we already have.  The
  1555.        * following allows an error of up to +/-.001
  1556.        */
  1557.       if (!png_colorspace_endpoints_match(xy, &colorspace->end_points_xy, 100))
  1558.       {
  1559.          colorspace->flags |= PNG_COLORSPACE_INVALID;
  1560.          png_benign_error(png_ptr, "inconsistent chromaticities");
  1561.          return 0; /* failed */
  1562.       }
  1563.  
  1564.       /* Only overwrite with preferred values */
  1565.       if (!preferred)
  1566.          return 1; /* ok, but no change */
  1567.    }
  1568.  
  1569.    colorspace->end_points_xy = *xy;
  1570.    colorspace->end_points_XYZ = *XYZ;
  1571.    colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS;
  1572.  
  1573.    /* The end points are normally quoted to two decimal digits, so allow +/-0.01
  1574.     * on this test.
  1575.     */
  1576.    if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000))
  1577.       colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB;
  1578.  
  1579.    else
  1580.       colorspace->flags &= PNG_COLORSPACE_CANCEL(
  1581.          PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);
  1582.  
  1583.    return 2; /* ok and changed */
  1584. }
  1585.  
  1586. int /* PRIVATE */
  1587. png_colorspace_set_chromaticities(png_const_structrp png_ptr,
  1588.    png_colorspacerp colorspace, const png_xy *xy, int preferred)
  1589. {
  1590.    /* We must check the end points to ensure they are reasonable - in the past
  1591.     * color management systems have crashed as a result of getting bogus
  1592.     * colorant values, while this isn't the fault of libpng it is the
  1593.     * responsibility of libpng because PNG carries the bomb and libpng is in a
  1594.     * position to protect against it.
  1595.     */
  1596.    png_XYZ XYZ;
  1597.  
  1598.    switch (png_colorspace_check_xy(&XYZ, xy))
  1599.    {
  1600.       case 0: /* success */
  1601.          return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,
  1602.             preferred);
  1603.  
  1604.       case 1:
  1605.          /* We can't invert the chromaticities so we can't produce value XYZ
  1606.           * values.  Likely as not a color management system will fail too.
  1607.           */
  1608.          colorspace->flags |= PNG_COLORSPACE_INVALID;
  1609.          png_benign_error(png_ptr, "invalid chromaticities");
  1610.          break;
  1611.  
  1612.       default:
  1613.          /* libpng is broken; this should be a warning but if it happens we
  1614.           * want error reports so for the moment it is an error.
  1615.           */
  1616.          colorspace->flags |= PNG_COLORSPACE_INVALID;
  1617.          png_error(png_ptr, "internal error checking chromaticities");
  1618.          break;
  1619.    }
  1620.  
  1621.    return 0; /* failed */
  1622. }
  1623.  
  1624. int /* PRIVATE */
  1625. png_colorspace_set_endpoints(png_const_structrp png_ptr,
  1626.    png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)
  1627. {
  1628.    png_XYZ XYZ = *XYZ_in;
  1629.    png_xy xy;
  1630.  
  1631.    switch (png_colorspace_check_XYZ(&xy, &XYZ))
  1632.    {
  1633.       case 0:
  1634.          return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,
  1635.             preferred);
  1636.  
  1637.       case 1:
  1638.          /* End points are invalid. */
  1639.          colorspace->flags |= PNG_COLORSPACE_INVALID;
  1640.          png_benign_error(png_ptr, "invalid end points");
  1641.          break;
  1642.  
  1643.       default:
  1644.          colorspace->flags |= PNG_COLORSPACE_INVALID;
  1645.          png_error(png_ptr, "internal error checking chromaticities");
  1646.          break;
  1647.    }
  1648.  
  1649.    return 0; /* failed */
  1650. }
  1651.  
  1652. #if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED)
  1653. /* Error message generation */
  1654. static char
  1655. png_icc_tag_char(png_uint_32 byte)
  1656. {
  1657.    byte &= 0xff;
  1658.    if (byte >= 32 && byte <= 126)
  1659.       return (char)byte;
  1660.    else
  1661.       return '?';
  1662. }
  1663.  
  1664. static void
  1665. png_icc_tag_name(char *name, png_uint_32 tag)
  1666. {
  1667.    name[0] = '\'';
  1668.    name[1] = png_icc_tag_char(tag >> 24);
  1669.    name[2] = png_icc_tag_char(tag >> 16);
  1670.    name[3] = png_icc_tag_char(tag >>  8);
  1671.    name[4] = png_icc_tag_char(tag      );
  1672.    name[5] = '\'';
  1673. }
  1674.  
  1675. static int
  1676. is_ICC_signature_char(png_alloc_size_t it)
  1677. {
  1678.    return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) ||
  1679.       (it >= 97 && it <= 122);
  1680. }
  1681.  
  1682. static int is_ICC_signature(png_alloc_size_t it)
  1683. {
  1684.    return is_ICC_signature_char(it >> 24) /* checks all the top bits */ &&
  1685.       is_ICC_signature_char((it >> 16) & 0xff) &&
  1686.       is_ICC_signature_char((it >> 8) & 0xff) &&
  1687.       is_ICC_signature_char(it & 0xff);
  1688. }
  1689.  
  1690. static int
  1691. png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace,
  1692.    png_const_charp name, png_alloc_size_t value, png_const_charp reason)
  1693. {
  1694.    size_t pos;
  1695.    char message[196]; /* see below for calculation */
  1696.  
  1697.    if (colorspace != NULL)
  1698.       colorspace->flags |= PNG_COLORSPACE_INVALID;
  1699.  
  1700.    pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */
  1701.    pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */
  1702.    pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */
  1703.    if (is_ICC_signature(value))
  1704.    {
  1705.       /* So 'value' is at most 4 bytes and the following cast is safe */
  1706.       png_icc_tag_name(message+pos, (png_uint_32)value);
  1707.       pos += 6; /* total +8; less than the else clause */
  1708.       message[pos++] = ':';
  1709.       message[pos++] = ' ';
  1710.    }
  1711. #  ifdef PNG_WARNINGS_SUPPORTED
  1712.    else
  1713.       {
  1714.          char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/
  1715.  
  1716.          pos = png_safecat(message, (sizeof message), pos,
  1717.             png_format_number(number, number+(sizeof number),
  1718.                PNG_NUMBER_FORMAT_x, value));
  1719.          pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/
  1720.       }
  1721. #  endif
  1722.    /* The 'reason' is an arbitrary message, allow +79 maximum 195 */
  1723.    pos = png_safecat(message, (sizeof message), pos, reason);
  1724.  
  1725.    /* This is recoverable, but make it unconditionally an app_error on write to
  1726.     * avoid writing invalid ICC profiles into PNG files.  (I.e.  we handle them
  1727.     * on read, with a warning, but on write unless the app turns off
  1728.     * application errors the PNG won't be written.)
  1729.     */
  1730.    png_chunk_report(png_ptr, message,
  1731.       (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);
  1732.  
  1733.    return 0;
  1734. }
  1735. #endif /* sRGB || iCCP */
  1736.  
  1737. #ifdef PNG_sRGB_SUPPORTED
  1738. int /* PRIVATE */
  1739. png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,
  1740.    int intent)
  1741. {
  1742.    /* sRGB sets known gamma, end points and (from the chunk) intent. */
  1743.    /* IMPORTANT: these are not necessarily the values found in an ICC profile
  1744.     * because ICC profiles store values adapted to a D50 environment; it is
  1745.     * expected that the ICC profile mediaWhitePointTag will be D50, see the
  1746.     * checks and code elsewhere to understand this better.
  1747.     *
  1748.     * These XYZ values, which are accurate to 5dp, produce rgb to gray
  1749.     * coefficients of (6968,23435,2366), which are reduced (because they add up
  1750.     * to 32769 not 32768) to (6968,23434,2366).  These are the values that
  1751.     * libpng has traditionally used (and are the best values given the 15bit
  1752.     * algorithm used by the rgb to gray code.)
  1753.     */
  1754.    static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */
  1755.    {
  1756.       /* color      X      Y      Z */
  1757.       /* red   */ 41239, 21264,  1933,
  1758.       /* green */ 35758, 71517, 11919,
  1759.       /* blue  */ 18048,  7219, 95053
  1760.    };
  1761.  
  1762.    /* Do nothing if the colorspace is already invalidated. */
  1763.    if (colorspace->flags & PNG_COLORSPACE_INVALID)
  1764.       return 0;
  1765.  
  1766.    /* Check the intent, then check for existing settings.  It is valid for the
  1767.     * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must
  1768.     * be consistent with the correct values.  If, however, this function is
  1769.     * called below because an iCCP chunk matches sRGB then it is quite
  1770.     * conceivable that an older app recorded incorrect gAMA and cHRM because of
  1771.     * an incorrect calculation based on the values in the profile - this does
  1772.     * *not* invalidate the profile (though it still produces an error, which can
  1773.     * be ignored.)
  1774.     */
  1775.    if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)
  1776.       return png_icc_profile_error(png_ptr, colorspace, "sRGB",
  1777.          (unsigned)intent, "invalid sRGB rendering intent");
  1778.  
  1779.    if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&
  1780.       colorspace->rendering_intent != intent)
  1781.       return png_icc_profile_error(png_ptr, colorspace, "sRGB",
  1782.          (unsigned)intent, "inconsistent rendering intents");
  1783.  
  1784.    if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)
  1785.    {
  1786.       png_benign_error(png_ptr, "duplicate sRGB information ignored");
  1787.       return 0;
  1788.    }
  1789.  
  1790.    /* If the standard sRGB cHRM chunk does not match the one from the PNG file
  1791.     * warn but overwrite the value with the correct one.
  1792.     */
  1793.    if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&
  1794.       !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,
  1795.          100))
  1796.       png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",
  1797.          PNG_CHUNK_ERROR);
  1798.  
  1799.    /* This check is just done for the error reporting - the routine always
  1800.     * returns true when the 'from' argument corresponds to sRGB (2).
  1801.     */
  1802.    (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,
  1803.       2/*from sRGB*/);
  1804.  
  1805.    /* intent: bugs in GCC force 'int' to be used as the parameter type. */
  1806.    colorspace->rendering_intent = (png_uint_16)intent;
  1807.    colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT;
  1808.  
  1809.    /* endpoints */
  1810.    colorspace->end_points_xy = sRGB_xy;
  1811.    colorspace->end_points_XYZ = sRGB_XYZ;
  1812.    colorspace->flags |=
  1813.       (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);
  1814.  
  1815.    /* gamma */
  1816.    colorspace->gamma = PNG_GAMMA_sRGB_INVERSE;
  1817.    colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA;
  1818.  
  1819.    /* Finally record that we have an sRGB profile */
  1820.    colorspace->flags |=
  1821.       (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);
  1822.  
  1823.    return 1; /* set */
  1824. }
  1825. #endif /* sRGB */
  1826.  
  1827. #ifdef PNG_iCCP_SUPPORTED
  1828. /* Encoded value of D50 as an ICC XYZNumber.  From the ICC 2010 spec the value
  1829.  * is XYZ(0.9642,1.0,0.8249), which scales to:
  1830.  *
  1831.  *    (63189.8112, 65536, 54060.6464)
  1832.  */
  1833. static const png_byte D50_nCIEXYZ[12] =
  1834.    { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };
  1835.  
  1836. int /* PRIVATE */
  1837. png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
  1838.    png_const_charp name, png_uint_32 profile_length)
  1839. {
  1840.    if (profile_length < 132)
  1841.       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
  1842.          "too short");
  1843.  
  1844.    if (profile_length & 3)
  1845.       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
  1846.          "invalid length");
  1847.  
  1848.    return 1;
  1849. }
  1850.  
  1851. int /* PRIVATE */
  1852. png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
  1853.    png_const_charp name, png_uint_32 profile_length,
  1854.    png_const_bytep profile/* first 132 bytes only */, int color_type)
  1855. {
  1856.    png_uint_32 temp;
  1857.  
  1858.    /* Length check; this cannot be ignored in this code because profile_length
  1859.     * is used later to check the tag table, so even if the profile seems over
  1860.     * long profile_length from the caller must be correct.  The caller can fix
  1861.     * this up on read or write by just passing in the profile header length.
  1862.     */
  1863.    temp = png_get_uint_32(profile);
  1864.    if (temp != profile_length)
  1865.       return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1866.          "length does not match profile");
  1867.  
  1868.    temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */
  1869.    if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */
  1870.       profile_length < 132+12*temp) /* truncated tag table */
  1871.       return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1872.          "tag count too large");
  1873.  
  1874.    /* The 'intent' must be valid or we can't store it, ICC limits the intent to
  1875.     * 16 bits.
  1876.     */
  1877.    temp = png_get_uint_32(profile+64);
  1878.    if (temp >= 0xffff) /* The ICC limit */
  1879.       return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1880.          "invalid rendering intent");
  1881.  
  1882.    /* This is just a warning because the profile may be valid in future
  1883.     * versions.
  1884.     */
  1885.    if (temp >= PNG_sRGB_INTENT_LAST)
  1886.       (void)png_icc_profile_error(png_ptr, NULL, name, temp,
  1887.          "intent outside defined range");
  1888.  
  1889.    /* At this point the tag table can't be checked because it hasn't necessarily
  1890.     * been loaded; however, various header fields can be checked.  These checks
  1891.     * are for values permitted by the PNG spec in an ICC profile; the PNG spec
  1892.     * restricts the profiles that can be passed in an iCCP chunk (they must be
  1893.     * appropriate to processing PNG data!)
  1894.     */
  1895.  
  1896.    /* Data checks (could be skipped).  These checks must be independent of the
  1897.     * version number; however, the version number doesn't accomodate changes in
  1898.     * the header fields (just the known tags and the interpretation of the
  1899.     * data.)
  1900.     */
  1901.    temp = png_get_uint_32(profile+36); /* signature 'ascp' */
  1902.    if (temp != 0x61637370)
  1903.       return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1904.          "invalid signature");
  1905.  
  1906.    /* Currently the PCS illuminant/adopted white point (the computational
  1907.     * white point) are required to be D50,
  1908.     * however the profile contains a record of the illuminant so perhaps ICC
  1909.     * expects to be able to change this in the future (despite the rationale in
  1910.     * the introduction for using a fixed PCS adopted white.)  Consequently the
  1911.     * following is just a warning.
  1912.     */
  1913.    if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0)
  1914.       (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/,
  1915.          "PCS illuminant is not D50");
  1916.  
  1917.    /* The PNG spec requires this:
  1918.     * "If the iCCP chunk is present, the image samples conform to the colour
  1919.     * space represented by the embedded ICC profile as defined by the
  1920.     * International Color Consortium [ICC]. The colour space of the ICC profile
  1921.     * shall be an RGB colour space for colour images (PNG colour types 2, 3, and
  1922.     * 6), or a greyscale colour space for greyscale images (PNG colour types 0
  1923.     * and 4)."
  1924.     *
  1925.     * This checking code ensures the embedded profile (on either read or write)
  1926.     * conforms to the specification requirements.  Notice that an ICC 'gray'
  1927.     * color-space profile contains the information to transform the monochrome
  1928.     * data to XYZ or L*a*b (according to which PCS the profile uses) and this
  1929.     * should be used in preference to the standard libpng K channel replication
  1930.     * into R, G and B channels.
  1931.     *
  1932.     * Previously it was suggested that an RGB profile on grayscale data could be
  1933.     * handled.  However it it is clear that using an RGB profile in this context
  1934.     * must be an error - there is no specification of what it means.  Thus it is
  1935.     * almost certainly more correct to ignore the profile.
  1936.     */
  1937.    temp = png_get_uint_32(profile+16); /* data colour space field */
  1938.    switch (temp)
  1939.    {
  1940.       case 0x52474220: /* 'RGB ' */
  1941.          if (!(color_type & PNG_COLOR_MASK_COLOR))
  1942.             return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1943.                "RGB color space not permitted on grayscale PNG");
  1944.          break;
  1945.  
  1946.       case 0x47524159: /* 'GRAY' */
  1947.          if (color_type & PNG_COLOR_MASK_COLOR)
  1948.             return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1949.                "Gray color space not permitted on RGB PNG");
  1950.          break;
  1951.  
  1952.       default:
  1953.          return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1954.             "invalid ICC profile color space");
  1955.    }
  1956.  
  1957.    /* It is up to the application to check that the profile class matches the
  1958.     * application requirements; the spec provides no guidance, but it's pretty
  1959.     * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer
  1960.     * ('prtr') or 'spac' (for generic color spaces).  Issue a warning in these
  1961.     * cases.  Issue an error for device link or abstract profiles - these don't
  1962.     * contain the records necessary to transform the color-space to anything
  1963.     * other than the target device (and not even that for an abstract profile).
  1964.     * Profiles of these classes may not be embedded in images.
  1965.     */
  1966.    temp = png_get_uint_32(profile+12); /* profile/device class */
  1967.    switch (temp)
  1968.    {
  1969.       case 0x73636E72: /* 'scnr' */
  1970.       case 0x6D6E7472: /* 'mntr' */
  1971.       case 0x70727472: /* 'prtr' */
  1972.       case 0x73706163: /* 'spac' */
  1973.          /* All supported */
  1974.          break;
  1975.  
  1976.       case 0x61627374: /* 'abst' */
  1977.          /* May not be embedded in an image */
  1978.          return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1979.             "invalid embedded Abstract ICC profile");
  1980.  
  1981.       case 0x6C696E6B: /* 'link' */
  1982.          /* DeviceLink profiles cannnot be interpreted in a non-device specific
  1983.           * fashion, if an app uses the AToB0Tag in the profile the results are
  1984.           * undefined unless the result is sent to the intended device,
  1985.           * therefore a DeviceLink profile should not be found embedded in a
  1986.           * PNG.
  1987.           */
  1988.          return png_icc_profile_error(png_ptr, colorspace, name, temp,
  1989.             "unexpected DeviceLink ICC profile class");
  1990.  
  1991.       case 0x6E6D636C: /* 'nmcl' */
  1992.          /* A NamedColor profile is also device specific, however it doesn't
  1993.           * contain an AToB0 tag that is open to misintrepretation.  Almost
  1994.           * certainly it will fail the tests below.
  1995.           */
  1996.          (void)png_icc_profile_error(png_ptr, NULL, name, temp,
  1997.             "unexpected NamedColor ICC profile class");
  1998.          break;
  1999.  
  2000.       default:
  2001.          /* To allow for future enhancements to the profile accept unrecognized
  2002.           * profile classes with a warning, these then hit the test below on the
  2003.           * tag content to ensure they are backward compatible with one of the
  2004.           * understood profiles.
  2005.           */
  2006.          (void)png_icc_profile_error(png_ptr, NULL, name, temp,
  2007.             "unrecognized ICC profile class");
  2008.          break;
  2009.    }
  2010.  
  2011.    /* For any profile other than a device link one the PCS must be encoded
  2012.     * either in XYZ or Lab.
  2013.     */
  2014.    temp = png_get_uint_32(profile+20);
  2015.    switch (temp)
  2016.    {
  2017.       case 0x58595A20: /* 'XYZ ' */
  2018.       case 0x4C616220: /* 'Lab ' */
  2019.          break;
  2020.  
  2021.       default:
  2022.          return png_icc_profile_error(png_ptr, colorspace, name, temp,
  2023.             "unexpected ICC PCS encoding");
  2024.    }
  2025.  
  2026.    return 1;
  2027. }
  2028.  
  2029. int /* PRIVATE */
  2030. png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
  2031.    png_const_charp name, png_uint_32 profile_length,
  2032.    png_const_bytep profile /* header plus whole tag table */)
  2033. {
  2034.    png_uint_32 tag_count = png_get_uint_32(profile+128);
  2035.    png_uint_32 itag;
  2036.    png_const_bytep tag = profile+132; /* The first tag */
  2037.  
  2038.    /* First scan all the tags in the table and add bits to the icc_info value
  2039.     * (temporarily in 'tags').
  2040.     */
  2041.    for (itag=0; itag < tag_count; ++itag, tag += 12)
  2042.    {
  2043.       png_uint_32 tag_id = png_get_uint_32(tag+0);
  2044.       png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */
  2045.       png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */
  2046.  
  2047.       /* The ICC specification does not exclude zero length tags, therefore the
  2048.        * start might actually be anywhere if there is no data, but this would be
  2049.        * a clear abuse of the intent of the standard so the start is checked for
  2050.        * being in range.  All defined tag types have an 8 byte header - a 4 byte
  2051.        * type signature then 0.
  2052.        */
  2053.       if ((tag_start & 3) != 0)
  2054.       {
  2055.          /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is
  2056.           * only a warning here because libpng does not care about the
  2057.           * alignment.
  2058.           */
  2059.          (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,
  2060.             "ICC profile tag start not a multiple of 4");
  2061.       }
  2062.  
  2063.       /* This is a hard error; potentially it can cause read outside the
  2064.        * profile.
  2065.        */
  2066.       if (tag_start > profile_length || tag_length > profile_length - tag_start)
  2067.          return png_icc_profile_error(png_ptr, colorspace, name, tag_id,
  2068.             "ICC profile tag outside profile");
  2069.    }
  2070.  
  2071.    return 1; /* success, maybe with warnings */
  2072. }
  2073.  
  2074. #ifdef PNG_sRGB_SUPPORTED
  2075. /* Information about the known ICC sRGB profiles */
  2076. static const struct
  2077. {
  2078.    png_uint_32 adler, crc, length;
  2079.    png_uint_32 md5[4];
  2080.    png_byte    have_md5;
  2081.    png_byte    is_broken;
  2082.    png_uint_16 intent;
  2083.  
  2084. #  define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)
  2085. #  define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\
  2086.       { adler, crc, length, md5, broke, intent },
  2087.  
  2088. } png_sRGB_checks[] =
  2089. {
  2090.    /* This data comes from contrib/tools/checksum-icc run on downloads of
  2091.     * all four ICC sRGB profiles from www.color.org.
  2092.     */
  2093.    /* adler32, crc32, MD5[4], intent, date, length, file-name */
  2094.    PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,
  2095.       PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
  2096.       "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
  2097.  
  2098.    /* ICC sRGB v2 perceptual no black-compensation: */
  2099.    PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
  2100.       PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
  2101.       "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
  2102.  
  2103.    PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
  2104.       PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
  2105.       "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
  2106.  
  2107.    /* ICC sRGB v4 perceptual */
  2108.    PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
  2109.       PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
  2110.       "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
  2111.  
  2112.    /* The following profiles have no known MD5 checksum. If there is a match
  2113.     * on the (empty) MD5 the other fields are used to attempt a match and
  2114.     * a warning is produced.  The first two of these profiles have a 'cprt' tag
  2115.     * which suggests that they were also made by Hewlett Packard.
  2116.     */
  2117.    PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
  2118.       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
  2119.       "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
  2120.  
  2121.    /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not
  2122.     * match the D50 PCS illuminant in the header (it is in fact the D65 values,
  2123.     * so the white point is recorded as the un-adapted value.)  The profiles
  2124.     * below only differ in one byte - the intent - and are basically the same as
  2125.     * the previous profile except for the mediaWhitePointTag error and a missing
  2126.     * chromaticAdaptationTag.
  2127.     */
  2128.    PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
  2129.       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
  2130.       "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")
  2131.  
  2132.    PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,
  2133.       PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
  2134.       "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
  2135. };
  2136.  
  2137. static int
  2138. png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
  2139.    png_const_bytep profile, uLong adler)
  2140. {
  2141.    /* The quick check is to verify just the MD5 signature and trust the
  2142.     * rest of the data.  Because the profile has already been verified for
  2143.     * correctness this is safe.  png_colorspace_set_sRGB will check the 'intent'
  2144.     * field too, so if the profile has been edited with an intent not defined
  2145.     * by sRGB (but maybe defined by a later ICC specification) the read of
  2146.     * the profile will fail at that point.
  2147.     */
  2148.    png_uint_32 length = 0;
  2149.    png_uint_32 intent = 0x10000; /* invalid */
  2150. #if PNG_sRGB_PROFILE_CHECKS > 1
  2151.    uLong crc = 0; /* the value for 0 length data */
  2152. #endif
  2153.    unsigned int i;
  2154.  
  2155.    for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)
  2156.    {
  2157.       if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&
  2158.          png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&
  2159.          png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&
  2160.          png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])
  2161.       {
  2162.          /* This may be one of the old HP profiles without an MD5, in that
  2163.           * case we can only use the length and Adler32 (note that these
  2164.           * are not used by default if there is an MD5!)
  2165.           */
  2166. #        if PNG_sRGB_PROFILE_CHECKS == 0
  2167.             if (png_sRGB_checks[i].have_md5)
  2168.                return 1+png_sRGB_checks[i].is_broken;
  2169. #        endif
  2170.  
  2171.          /* Profile is unsigned or more checks have been configured in. */
  2172.          if (length == 0)
  2173.          {
  2174.             length = png_get_uint_32(profile);
  2175.             intent = png_get_uint_32(profile+64);
  2176.          }
  2177.  
  2178.          /* Length *and* intent must match */
  2179.          if (length == png_sRGB_checks[i].length &&
  2180.             intent == png_sRGB_checks[i].intent)
  2181.          {
  2182.             /* Now calculate the adler32 if not done already. */
  2183.             if (adler == 0)
  2184.             {
  2185.                adler = adler32(0, NULL, 0);
  2186.                adler = adler32(adler, profile, length);
  2187.             }
  2188.  
  2189.             if (adler == png_sRGB_checks[i].adler)
  2190.             {
  2191.                /* These basic checks suggest that the data has not been
  2192.                 * modified, but if the check level is more than 1 perform
  2193.                 * our own crc32 checksum on the data.
  2194.                 */
  2195. #              if PNG_sRGB_PROFILE_CHECKS > 1
  2196.                   if (crc == 0)
  2197.                   {
  2198.                      crc = crc32(0, NULL, 0);
  2199.                      crc = crc32(crc, profile, length);
  2200.                   }
  2201.  
  2202.                   /* So this check must pass for the 'return' below to happen.
  2203.                    */
  2204.                   if (crc == png_sRGB_checks[i].crc)
  2205. #              endif
  2206.                {
  2207.                   if (png_sRGB_checks[i].is_broken)
  2208.                   {
  2209.                      /* These profiles are known to have bad data that may cause
  2210.                       * problems if they are used, therefore attempt to
  2211.                       * discourage their use, skip the 'have_md5' warning below,
  2212.                       * which is made irrelevant by this error.
  2213.                       */
  2214.                      png_chunk_report(png_ptr, "known incorrect sRGB profile",
  2215.                         PNG_CHUNK_ERROR);
  2216.                   }
  2217.  
  2218.                   /* Warn that this being done; this isn't even an error since
  2219.                    * the profile is perfectly valid, but it would be nice if
  2220.                    * people used the up-to-date ones.
  2221.                    */
  2222.                   else if (!png_sRGB_checks[i].have_md5)
  2223.                   {
  2224.                      png_chunk_report(png_ptr,
  2225.                         "out-of-date sRGB profile with no signature",
  2226.                         PNG_CHUNK_WARNING);
  2227.                   }
  2228.  
  2229.                   return 1+png_sRGB_checks[i].is_broken;
  2230.                }
  2231.             }
  2232.          }
  2233.  
  2234. #        if PNG_sRGB_PROFILE_CHECKS > 0
  2235.             /* The signature matched, but the profile had been changed in some
  2236.              * way.  This is an apparent violation of the ICC terms of use and,
  2237.              * anyway, probably indicates a data error or uninformed hacking.
  2238.              */
  2239.             if (png_sRGB_checks[i].have_md5)
  2240.                png_benign_error(png_ptr,
  2241.                   "copyright violation: edited ICC profile ignored");
  2242. #        endif
  2243.       }
  2244.    }
  2245.  
  2246.    return 0; /* no match */
  2247. }
  2248. #endif
  2249.  
  2250. #ifdef PNG_sRGB_SUPPORTED
  2251. void /* PRIVATE */
  2252. png_icc_set_sRGB(png_const_structrp png_ptr,
  2253.    png_colorspacerp colorspace, png_const_bytep profile, uLong adler)
  2254. {
  2255.    /* Is this profile one of the known ICC sRGB profiles?  If it is, just set
  2256.     * the sRGB information.
  2257.     */
  2258.    if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler))
  2259.       (void)png_colorspace_set_sRGB(png_ptr, colorspace,
  2260.          (int)/*already checked*/png_get_uint_32(profile+64));
  2261. }
  2262. #endif /* PNG_READ_sRGB_SUPPORTED */
  2263.  
  2264. int /* PRIVATE */
  2265. png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,
  2266.    png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,
  2267.    int color_type)
  2268. {
  2269.    if (colorspace->flags & PNG_COLORSPACE_INVALID)
  2270.       return 0;
  2271.  
  2272.    if (png_icc_check_length(png_ptr, colorspace, name, profile_length) &&
  2273.       png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,
  2274.          color_type) &&
  2275.       png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
  2276.          profile))
  2277.    {
  2278. #     ifdef PNG_sRGB_SUPPORTED
  2279.          /* If no sRGB support, don't try storing sRGB information */
  2280.          png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
  2281. #     endif
  2282.       return 1;
  2283.    }
  2284.  
  2285.    /* Failure case */
  2286.    return 0;
  2287. }
  2288. #endif /* iCCP */
  2289.  
  2290. #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
  2291. void /* PRIVATE */
  2292. png_colorspace_set_rgb_coefficients(png_structrp png_ptr)
  2293. {
  2294.    /* Set the rgb_to_gray coefficients from the colorspace. */
  2295.    if (!png_ptr->rgb_to_gray_coefficients_set &&
  2296.       (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
  2297.    {
  2298.       /* png_set_background has not been called, get the coefficients from the Y
  2299.        * values of the colorspace colorants.
  2300.        */
  2301.       png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y;
  2302.       png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y;
  2303.       png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y;
  2304.       png_fixed_point total = r+g+b;
  2305.  
  2306.       if (total > 0 &&
  2307.          r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 &&
  2308.          g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 &&
  2309.          b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 &&
  2310.          r+g+b <= 32769)
  2311.       {
  2312.          /* We allow 0 coefficients here.  r+g+b may be 32769 if two or
  2313.           * all of the coefficients were rounded up.  Handle this by
  2314.           * reducing the *largest* coefficient by 1; this matches the
  2315.           * approach used for the default coefficients in pngrtran.c
  2316.           */
  2317.          int add = 0;
  2318.  
  2319.          if (r+g+b > 32768)
  2320.             add = -1;
  2321.          else if (r+g+b < 32768)
  2322.             add = 1;
  2323.  
  2324.          if (add != 0)
  2325.          {
  2326.             if (g >= r && g >= b)
  2327.                g += add;
  2328.             else if (r >= g && r >= b)
  2329.                r += add;
  2330.             else
  2331.                b += add;
  2332.          }
  2333.  
  2334.          /* Check for an internal error. */
  2335.          if (r+g+b != 32768)
  2336.             png_error(png_ptr,
  2337.                "internal error handling cHRM coefficients");
  2338.  
  2339.          else
  2340.          {
  2341.             png_ptr->rgb_to_gray_red_coeff   = (png_uint_16)r;
  2342.             png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;
  2343.          }
  2344.       }
  2345.  
  2346.       /* This is a png_error at present even though it could be ignored -
  2347.        * it should never happen, but it is important that if it does, the
  2348.        * bug is fixed.
  2349.        */
  2350.       else
  2351.          png_error(png_ptr, "internal error handling cHRM->XYZ");
  2352.    }
  2353. }
  2354. #endif
  2355.  
  2356. #endif /* COLORSPACE */
  2357.  
  2358. void /* PRIVATE */
  2359. png_check_IHDR(png_const_structrp png_ptr,
  2360.    png_uint_32 width, png_uint_32 height, int bit_depth,
  2361.    int color_type, int interlace_type, int compression_type,
  2362.    int filter_type)
  2363. {
  2364.    int error = 0;
  2365.  
  2366.    /* Check for width and height valid values */
  2367.    if (width == 0)
  2368.    {
  2369.       png_warning(png_ptr, "Image width is zero in IHDR");
  2370.       error = 1;
  2371.    }
  2372.  
  2373.    if (height == 0)
  2374.    {
  2375.       png_warning(png_ptr, "Image height is zero in IHDR");
  2376.       error = 1;
  2377.    }
  2378.  
  2379. #  ifdef PNG_SET_USER_LIMITS_SUPPORTED
  2380.    if (width > png_ptr->user_width_max)
  2381.  
  2382. #  else
  2383.    if (width > PNG_USER_WIDTH_MAX)
  2384. #  endif
  2385.    {
  2386.       png_warning(png_ptr, "Image width exceeds user limit in IHDR");
  2387.       error = 1;
  2388.    }
  2389.  
  2390. #  ifdef PNG_SET_USER_LIMITS_SUPPORTED
  2391.    if (height > png_ptr->user_height_max)
  2392. #  else
  2393.    if (height > PNG_USER_HEIGHT_MAX)
  2394. #  endif
  2395.    {
  2396.       png_warning(png_ptr, "Image height exceeds user limit in IHDR");
  2397.       error = 1;
  2398.    }
  2399.  
  2400.    if (width > PNG_UINT_31_MAX)
  2401.    {
  2402.       png_warning(png_ptr, "Invalid image width in IHDR");
  2403.       error = 1;
  2404.    }
  2405.  
  2406.    if (height > PNG_UINT_31_MAX)
  2407.    {
  2408.       png_warning(png_ptr, "Invalid image height in IHDR");
  2409.       error = 1;
  2410.    }
  2411.  
  2412.    if (width > (PNG_UINT_32_MAX
  2413.                  >> 3)      /* 8-byte RGBA pixels */
  2414.                  - 48       /* bigrowbuf hack */
  2415.                  - 1        /* filter byte */
  2416.                  - 7*8      /* rounding of width to multiple of 8 pixels */
  2417.                  - 8)       /* extra max_pixel_depth pad */
  2418.       png_warning(png_ptr, "Width is too large for libpng to process pixels");
  2419.  
  2420.    /* Check other values */
  2421.    if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&
  2422.        bit_depth != 8 && bit_depth != 16)
  2423.    {
  2424.       png_warning(png_ptr, "Invalid bit depth in IHDR");
  2425.       error = 1;
  2426.    }
  2427.  
  2428.    if (color_type < 0 || color_type == 1 ||
  2429.        color_type == 5 || color_type > 6)
  2430.    {
  2431.       png_warning(png_ptr, "Invalid color type in IHDR");
  2432.       error = 1;
  2433.    }
  2434.  
  2435.    if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||
  2436.        ((color_type == PNG_COLOR_TYPE_RGB ||
  2437.          color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||
  2438.          color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))
  2439.    {
  2440.       png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");
  2441.       error = 1;
  2442.    }
  2443.  
  2444.    if (interlace_type >= PNG_INTERLACE_LAST)
  2445.    {
  2446.       png_warning(png_ptr, "Unknown interlace method in IHDR");
  2447.       error = 1;
  2448.    }
  2449.  
  2450.    if (compression_type != PNG_COMPRESSION_TYPE_BASE)
  2451.    {
  2452.       png_warning(png_ptr, "Unknown compression method in IHDR");
  2453.       error = 1;
  2454.    }
  2455.  
  2456. #  ifdef PNG_MNG_FEATURES_SUPPORTED
  2457.    /* Accept filter_method 64 (intrapixel differencing) only if
  2458.     * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
  2459.     * 2. Libpng did not read a PNG signature (this filter_method is only
  2460.     *    used in PNG datastreams that are embedded in MNG datastreams) and
  2461.     * 3. The application called png_permit_mng_features with a mask that
  2462.     *    included PNG_FLAG_MNG_FILTER_64 and
  2463.     * 4. The filter_method is 64 and
  2464.     * 5. The color_type is RGB or RGBA
  2465.     */
  2466.    if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) &&
  2467.        png_ptr->mng_features_permitted)
  2468.       png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
  2469.  
  2470.    if (filter_type != PNG_FILTER_TYPE_BASE)
  2471.    {
  2472.       if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
  2473.           (filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&
  2474.           ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
  2475.           (color_type == PNG_COLOR_TYPE_RGB ||
  2476.           color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
  2477.       {
  2478.          png_warning(png_ptr, "Unknown filter method in IHDR");
  2479.          error = 1;
  2480.       }
  2481.  
  2482.       if (png_ptr->mode & PNG_HAVE_PNG_SIGNATURE)
  2483.       {
  2484.          png_warning(png_ptr, "Invalid filter method in IHDR");
  2485.          error = 1;
  2486.       }
  2487.    }
  2488.  
  2489. #  else
  2490.    if (filter_type != PNG_FILTER_TYPE_BASE)
  2491.    {
  2492.       png_warning(png_ptr, "Unknown filter method in IHDR");
  2493.       error = 1;
  2494.    }
  2495. #  endif
  2496.  
  2497.    if (error == 1)
  2498.       png_error(png_ptr, "Invalid IHDR data");
  2499. }
  2500.  
  2501. #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
  2502. /* ASCII to fp functions */
  2503. /* Check an ASCII formated floating point value, see the more detailed
  2504.  * comments in pngpriv.h
  2505.  */
  2506. /* The following is used internally to preserve the sticky flags */
  2507. #define png_fp_add(state, flags) ((state) |= (flags))
  2508. #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
  2509.  
  2510. int /* PRIVATE */
  2511. png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
  2512.    png_size_tp whereami)
  2513. {
  2514.    int state = *statep;
  2515.    png_size_t i = *whereami;
  2516.  
  2517.    while (i < size)
  2518.    {
  2519.       int type;
  2520.       /* First find the type of the next character */
  2521.       switch (string[i])
  2522.       {
  2523.       case 43:  type = PNG_FP_SAW_SIGN;                   break;
  2524.       case 45:  type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;
  2525.       case 46:  type = PNG_FP_SAW_DOT;                    break;
  2526.       case 48:  type = PNG_FP_SAW_DIGIT;                  break;
  2527.       case 49: case 50: case 51: case 52:
  2528.       case 53: case 54: case 55: case 56:
  2529.       case 57:  type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;
  2530.       case 69:
  2531.       case 101: type = PNG_FP_SAW_E;                      break;
  2532.       default:  goto PNG_FP_End;
  2533.       }
  2534.  
  2535.       /* Now deal with this type according to the current
  2536.        * state, the type is arranged to not overlap the
  2537.        * bits of the PNG_FP_STATE.
  2538.        */
  2539.       switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
  2540.       {
  2541.       case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
  2542.          if (state & PNG_FP_SAW_ANY)
  2543.             goto PNG_FP_End; /* not a part of the number */
  2544.  
  2545.          png_fp_add(state, type);
  2546.          break;
  2547.  
  2548.       case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
  2549.          /* Ok as trailer, ok as lead of fraction. */
  2550.          if (state & PNG_FP_SAW_DOT) /* two dots */
  2551.             goto PNG_FP_End;
  2552.  
  2553.          else if (state & PNG_FP_SAW_DIGIT) /* trailing dot? */
  2554.             png_fp_add(state, type);
  2555.  
  2556.          else
  2557.             png_fp_set(state, PNG_FP_FRACTION | type);
  2558.  
  2559.          break;
  2560.  
  2561.       case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
  2562.          if (state & PNG_FP_SAW_DOT) /* delayed fraction */
  2563.             png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);
  2564.  
  2565.          png_fp_add(state, type | PNG_FP_WAS_VALID);
  2566.  
  2567.          break;
  2568.  
  2569.       case PNG_FP_INTEGER + PNG_FP_SAW_E:
  2570.          if ((state & PNG_FP_SAW_DIGIT) == 0)
  2571.             goto PNG_FP_End;
  2572.  
  2573.          png_fp_set(state, PNG_FP_EXPONENT);
  2574.  
  2575.          break;
  2576.  
  2577.    /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
  2578.          goto PNG_FP_End; ** no sign in fraction */
  2579.  
  2580.    /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
  2581.          goto PNG_FP_End; ** Because SAW_DOT is always set */
  2582.  
  2583.       case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
  2584.          png_fp_add(state, type | PNG_FP_WAS_VALID);
  2585.          break;
  2586.  
  2587.       case PNG_FP_FRACTION + PNG_FP_SAW_E:
  2588.          /* This is correct because the trailing '.' on an
  2589.           * integer is handled above - so we can only get here
  2590.           * with the sequence ".E" (with no preceding digits).
  2591.           */
  2592.          if ((state & PNG_FP_SAW_DIGIT) == 0)
  2593.             goto PNG_FP_End;
  2594.  
  2595.          png_fp_set(state, PNG_FP_EXPONENT);
  2596.  
  2597.          break;
  2598.  
  2599.       case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
  2600.          if (state & PNG_FP_SAW_ANY)
  2601.             goto PNG_FP_End; /* not a part of the number */
  2602.  
  2603.          png_fp_add(state, PNG_FP_SAW_SIGN);
  2604.  
  2605.          break;
  2606.  
  2607.    /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
  2608.          goto PNG_FP_End; */
  2609.  
  2610.       case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
  2611.          png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);
  2612.  
  2613.          break;
  2614.  
  2615.    /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
  2616.          goto PNG_FP_End; */
  2617.  
  2618.       default: goto PNG_FP_End; /* I.e. break 2 */
  2619.       }
  2620.  
  2621.       /* The character seems ok, continue. */
  2622.       ++i;
  2623.    }
  2624.  
  2625. PNG_FP_End:
  2626.    /* Here at the end, update the state and return the correct
  2627.     * return code.
  2628.     */
  2629.    *statep = state;
  2630.    *whereami = i;
  2631.  
  2632.    return (state & PNG_FP_SAW_DIGIT) != 0;
  2633. }
  2634.  
  2635.  
  2636. /* The same but for a complete string. */
  2637. int
  2638. png_check_fp_string(png_const_charp string, png_size_t size)
  2639. {
  2640.    int        state=0;
  2641.    png_size_t char_index=0;
  2642.  
  2643.    if (png_check_fp_number(string, size, &state, &char_index) &&
  2644.       (char_index == size || string[char_index] == 0))
  2645.       return state /* must be non-zero - see above */;
  2646.  
  2647.    return 0; /* i.e. fail */
  2648. }
  2649. #endif /* pCAL or sCAL */
  2650.  
  2651. #ifdef PNG_sCAL_SUPPORTED
  2652. #  ifdef PNG_FLOATING_POINT_SUPPORTED
  2653. /* Utility used below - a simple accurate power of ten from an integral
  2654.  * exponent.
  2655.  */
  2656. static double
  2657. png_pow10(int power)
  2658. {
  2659.    int recip = 0;
  2660.    double d = 1;
  2661.  
  2662.    /* Handle negative exponent with a reciprocal at the end because
  2663.     * 10 is exact whereas .1 is inexact in base 2
  2664.     */
  2665.    if (power < 0)
  2666.    {
  2667.       if (power < DBL_MIN_10_EXP) return 0;
  2668.       recip = 1, power = -power;
  2669.    }
  2670.  
  2671.    if (power > 0)
  2672.    {
  2673.       /* Decompose power bitwise. */
  2674.       double mult = 10;
  2675.       do
  2676.       {
  2677.          if (power & 1) d *= mult;
  2678.          mult *= mult;
  2679.          power >>= 1;
  2680.       }
  2681.       while (power > 0);
  2682.  
  2683.       if (recip) d = 1/d;
  2684.    }
  2685.    /* else power is 0 and d is 1 */
  2686.  
  2687.    return d;
  2688. }
  2689.  
  2690. /* Function to format a floating point value in ASCII with a given
  2691.  * precision.
  2692.  */
  2693. void /* PRIVATE */
  2694. png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
  2695.     double fp, unsigned int precision)
  2696. {
  2697.    /* We use standard functions from math.h, but not printf because
  2698.     * that would require stdio.  The caller must supply a buffer of
  2699.     * sufficient size or we will png_error.  The tests on size and
  2700.     * the space in ascii[] consumed are indicated below.
  2701.     */
  2702.    if (precision < 1)
  2703.       precision = DBL_DIG;
  2704.  
  2705.    /* Enforce the limit of the implementation precision too. */
  2706.    if (precision > DBL_DIG+1)
  2707.       precision = DBL_DIG+1;
  2708.  
  2709.    /* Basic sanity checks */
  2710.    if (size >= precision+5) /* See the requirements below. */
  2711.    {
  2712.       if (fp < 0)
  2713.       {
  2714.          fp = -fp;
  2715.          *ascii++ = 45; /* '-'  PLUS 1 TOTAL 1 */
  2716.          --size;
  2717.       }
  2718.  
  2719.       if (fp >= DBL_MIN && fp <= DBL_MAX)
  2720.       {
  2721.          int exp_b10;       /* A base 10 exponent */
  2722.          double base;   /* 10^exp_b10 */
  2723.  
  2724.          /* First extract a base 10 exponent of the number,
  2725.           * the calculation below rounds down when converting
  2726.           * from base 2 to base 10 (multiply by log10(2) -
  2727.           * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
  2728.           * be increased.  Note that the arithmetic shift
  2729.           * performs a floor() unlike C arithmetic - using a
  2730.           * C multiply would break the following for negative
  2731.           * exponents.
  2732.           */
  2733.          (void)frexp(fp, &exp_b10); /* exponent to base 2 */
  2734.  
  2735.          exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */
  2736.  
  2737.          /* Avoid underflow here. */
  2738.          base = png_pow10(exp_b10); /* May underflow */
  2739.  
  2740.          while (base < DBL_MIN || base < fp)
  2741.          {
  2742.             /* And this may overflow. */
  2743.             double test = png_pow10(exp_b10+1);
  2744.  
  2745.             if (test <= DBL_MAX)
  2746.                ++exp_b10, base = test;
  2747.  
  2748.             else
  2749.                break;
  2750.          }
  2751.  
  2752.          /* Normalize fp and correct exp_b10, after this fp is in the
  2753.           * range [.1,1) and exp_b10 is both the exponent and the digit
  2754.           * *before* which the decimal point should be inserted
  2755.           * (starting with 0 for the first digit).  Note that this
  2756.           * works even if 10^exp_b10 is out of range because of the
  2757.           * test on DBL_MAX above.
  2758.           */
  2759.          fp /= base;
  2760.          while (fp >= 1) fp /= 10, ++exp_b10;
  2761.  
  2762.          /* Because of the code above fp may, at this point, be
  2763.           * less than .1, this is ok because the code below can
  2764.           * handle the leading zeros this generates, so no attempt
  2765.           * is made to correct that here.
  2766.           */
  2767.  
  2768.          {
  2769.             int czero, clead, cdigits;
  2770.             char exponent[10];
  2771.  
  2772.             /* Allow up to two leading zeros - this will not lengthen
  2773.              * the number compared to using E-n.
  2774.              */
  2775.             if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */
  2776.             {
  2777.                czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */
  2778.                exp_b10 = 0;      /* Dot added below before first output. */
  2779.             }
  2780.             else
  2781.                czero = 0;    /* No zeros to add */
  2782.  
  2783.             /* Generate the digit list, stripping trailing zeros and
  2784.              * inserting a '.' before a digit if the exponent is 0.
  2785.              */
  2786.             clead = czero; /* Count of leading zeros */
  2787.             cdigits = 0;   /* Count of digits in list. */
  2788.  
  2789.             do
  2790.             {
  2791.                double d;
  2792.  
  2793.                fp *= 10;
  2794.                /* Use modf here, not floor and subtract, so that
  2795.                 * the separation is done in one step.  At the end
  2796.                 * of the loop don't break the number into parts so
  2797.                 * that the final digit is rounded.
  2798.                 */
  2799.                if (cdigits+czero-clead+1 < (int)precision)
  2800.                   fp = modf(fp, &d);
  2801.  
  2802.                else
  2803.                {
  2804.                   d = floor(fp + .5);
  2805.  
  2806.                   if (d > 9)
  2807.                   {
  2808.                      /* Rounding up to 10, handle that here. */
  2809.                      if (czero > 0)
  2810.                      {
  2811.                         --czero, d = 1;
  2812.                         if (cdigits == 0) --clead;
  2813.                      }
  2814.                      else
  2815.                      {
  2816.                         while (cdigits > 0 && d > 9)
  2817.                         {
  2818.                            int ch = *--ascii;
  2819.  
  2820.                            if (exp_b10 != (-1))
  2821.                               ++exp_b10;
  2822.  
  2823.                            else if (ch == 46)
  2824.                            {
  2825.                               ch = *--ascii, ++size;
  2826.                               /* Advance exp_b10 to '1', so that the
  2827.                                * decimal point happens after the
  2828.                                * previous digit.
  2829.                                */
  2830.                               exp_b10 = 1;
  2831.                            }
  2832.  
  2833.                            --cdigits;
  2834.                            d = ch - 47;  /* I.e. 1+(ch-48) */
  2835.                         }
  2836.  
  2837.                         /* Did we reach the beginning? If so adjust the
  2838.                          * exponent but take into account the leading
  2839.                          * decimal point.
  2840.                          */
  2841.                         if (d > 9)  /* cdigits == 0 */
  2842.                         {
  2843.                            if (exp_b10 == (-1))
  2844.                            {
  2845.                               /* Leading decimal point (plus zeros?), if
  2846.                                * we lose the decimal point here it must
  2847.                                * be reentered below.
  2848.                                */
  2849.                               int ch = *--ascii;
  2850.  
  2851.                               if (ch == 46)
  2852.                                  ++size, exp_b10 = 1;
  2853.  
  2854.                               /* Else lost a leading zero, so 'exp_b10' is
  2855.                                * still ok at (-1)
  2856.                                */
  2857.                            }
  2858.                            else
  2859.                               ++exp_b10;
  2860.  
  2861.                            /* In all cases we output a '1' */
  2862.                            d = 1;
  2863.                         }
  2864.                      }
  2865.                   }
  2866.                   fp = 0; /* Guarantees termination below. */
  2867.                }
  2868.  
  2869.                if (d == 0)
  2870.                {
  2871.                   ++czero;
  2872.                   if (cdigits == 0) ++clead;
  2873.                }
  2874.                else
  2875.                {
  2876.                   /* Included embedded zeros in the digit count. */
  2877.                   cdigits += czero - clead;
  2878.                   clead = 0;
  2879.  
  2880.                   while (czero > 0)
  2881.                   {
  2882.                      /* exp_b10 == (-1) means we just output the decimal
  2883.                       * place - after the DP don't adjust 'exp_b10' any
  2884.                       * more!
  2885.                       */
  2886.                      if (exp_b10 != (-1))
  2887.                      {
  2888.                         if (exp_b10 == 0) *ascii++ = 46, --size;
  2889.                         /* PLUS 1: TOTAL 4 */
  2890.                         --exp_b10;
  2891.                      }
  2892.                      *ascii++ = 48, --czero;
  2893.                   }
  2894.  
  2895.                   if (exp_b10 != (-1))
  2896.                   {
  2897.                      if (exp_b10 == 0) *ascii++ = 46, --size; /* counted
  2898.                                                                  above */
  2899.                      --exp_b10;
  2900.                   }
  2901.                   *ascii++ = (char)(48 + (int)d), ++cdigits;
  2902.                }
  2903.             }
  2904.             while (cdigits+czero-clead < (int)precision && fp > DBL_MIN);
  2905.  
  2906.             /* The total output count (max) is now 4+precision */
  2907.  
  2908.             /* Check for an exponent, if we don't need one we are
  2909.              * done and just need to terminate the string.  At
  2910.              * this point exp_b10==(-1) is effectively if flag - it got
  2911.              * to '-1' because of the decrement after outputing
  2912.              * the decimal point above (the exponent required is
  2913.              * *not* -1!)
  2914.              */
  2915.             if (exp_b10 >= (-1) && exp_b10 <= 2)
  2916.             {
  2917.                /* The following only happens if we didn't output the
  2918.                 * leading zeros above for negative exponent, so this
  2919.                 * doest add to the digit requirement.  Note that the
  2920.                 * two zeros here can only be output if the two leading
  2921.                 * zeros were *not* output, so this doesn't increase
  2922.                 * the output count.
  2923.                 */
  2924.                while (--exp_b10 >= 0) *ascii++ = 48;
  2925.  
  2926.                *ascii = 0;
  2927.  
  2928.                /* Total buffer requirement (including the '\0') is
  2929.                 * 5+precision - see check at the start.
  2930.                 */
  2931.                return;
  2932.             }
  2933.  
  2934.             /* Here if an exponent is required, adjust size for
  2935.              * the digits we output but did not count.  The total
  2936.              * digit output here so far is at most 1+precision - no
  2937.              * decimal point and no leading or trailing zeros have
  2938.              * been output.
  2939.              */
  2940.             size -= cdigits;
  2941.  
  2942.             *ascii++ = 69, --size;    /* 'E': PLUS 1 TOTAL 2+precision */
  2943.  
  2944.             /* The following use of an unsigned temporary avoids ambiguities in
  2945.              * the signed arithmetic on exp_b10 and permits GCC at least to do
  2946.              * better optimization.
  2947.              */
  2948.             {
  2949.                unsigned int uexp_b10;
  2950.  
  2951.                if (exp_b10 < 0)
  2952.                {
  2953.                   *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */
  2954.                   uexp_b10 = -exp_b10;
  2955.                }
  2956.  
  2957.                else
  2958.                   uexp_b10 = exp_b10;
  2959.  
  2960.                cdigits = 0;
  2961.  
  2962.                while (uexp_b10 > 0)
  2963.                {
  2964.                   exponent[cdigits++] = (char)(48 + uexp_b10 % 10);
  2965.                   uexp_b10 /= 10;
  2966.                }
  2967.             }
  2968.  
  2969.             /* Need another size check here for the exponent digits, so
  2970.              * this need not be considered above.
  2971.              */
  2972.             if ((int)size > cdigits)
  2973.             {
  2974.                while (cdigits > 0) *ascii++ = exponent[--cdigits];
  2975.  
  2976.                *ascii = 0;
  2977.  
  2978.                return;
  2979.             }
  2980.          }
  2981.       }
  2982.       else if (!(fp >= DBL_MIN))
  2983.       {
  2984.          *ascii++ = 48; /* '0' */
  2985.          *ascii = 0;
  2986.          return;
  2987.       }
  2988.       else
  2989.       {
  2990.          *ascii++ = 105; /* 'i' */
  2991.          *ascii++ = 110; /* 'n' */
  2992.          *ascii++ = 102; /* 'f' */
  2993.          *ascii = 0;
  2994.          return;
  2995.       }
  2996.    }
  2997.  
  2998.    /* Here on buffer too small. */
  2999.    png_error(png_ptr, "ASCII conversion buffer too small");
  3000. }
  3001.  
  3002. #  endif /* FLOATING_POINT */
  3003.  
  3004. #  ifdef PNG_FIXED_POINT_SUPPORTED
  3005. /* Function to format a fixed point value in ASCII.
  3006.  */
  3007. void /* PRIVATE */
  3008. png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
  3009.     png_size_t size, png_fixed_point fp)
  3010. {
  3011.    /* Require space for 10 decimal digits, a decimal point, a minus sign and a
  3012.     * trailing \0, 13 characters:
  3013.     */
  3014.    if (size > 12)
  3015.    {
  3016.       png_uint_32 num;
  3017.  
  3018.       /* Avoid overflow here on the minimum integer. */
  3019.       if (fp < 0)
  3020.          *ascii++ = 45, --size, num = -fp;
  3021.       else
  3022.          num = fp;
  3023.  
  3024.       if (num <= 0x80000000) /* else overflowed */
  3025.       {
  3026.          unsigned int ndigits = 0, first = 16 /* flag value */;
  3027.          char digits[10];
  3028.  
  3029.          while (num)
  3030.          {
  3031.             /* Split the low digit off num: */
  3032.             unsigned int tmp = num/10;
  3033.             num -= tmp*10;
  3034.             digits[ndigits++] = (char)(48 + num);
  3035.             /* Record the first non-zero digit, note that this is a number
  3036.              * starting at 1, it's not actually the array index.
  3037.              */
  3038.             if (first == 16 && num > 0)
  3039.                first = ndigits;
  3040.             num = tmp;
  3041.          }
  3042.  
  3043.          if (ndigits > 0)
  3044.          {
  3045.             while (ndigits > 5) *ascii++ = digits[--ndigits];
  3046.             /* The remaining digits are fractional digits, ndigits is '5' or
  3047.              * smaller at this point.  It is certainly not zero.  Check for a
  3048.              * non-zero fractional digit:
  3049.              */
  3050.             if (first <= 5)
  3051.             {
  3052.                unsigned int i;
  3053.                *ascii++ = 46; /* decimal point */
  3054.                /* ndigits may be <5 for small numbers, output leading zeros
  3055.                 * then ndigits digits to first:
  3056.                 */
  3057.                i = 5;
  3058.                while (ndigits < i) *ascii++ = 48, --i;
  3059.                while (ndigits >= first) *ascii++ = digits[--ndigits];
  3060.                /* Don't output the trailing zeros! */
  3061.             }
  3062.          }
  3063.          else
  3064.             *ascii++ = 48;
  3065.  
  3066.          /* And null terminate the string: */
  3067.          *ascii = 0;
  3068.          return;
  3069.       }
  3070.    }
  3071.  
  3072.    /* Here on buffer too small. */
  3073.    png_error(png_ptr, "ASCII conversion buffer too small");
  3074. }
  3075. #   endif /* FIXED_POINT */
  3076. #endif /* READ_SCAL */
  3077.  
  3078. #if defined(PNG_FLOATING_POINT_SUPPORTED) && \
  3079.    !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
  3080.    (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
  3081.    defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
  3082.    defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
  3083.    (defined(PNG_sCAL_SUPPORTED) && \
  3084.    defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
  3085. png_fixed_point
  3086. png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
  3087. {
  3088.    double r = floor(100000 * fp + .5);
  3089.  
  3090.    if (r > 2147483647. || r < -2147483648.)
  3091.       png_fixed_error(png_ptr, text);
  3092.  
  3093.    return (png_fixed_point)r;
  3094. }
  3095. #endif
  3096.  
  3097. #if defined(PNG_READ_GAMMA_SUPPORTED) || \
  3098.     defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
  3099. /* muldiv functions */
  3100. /* This API takes signed arguments and rounds the result to the nearest
  3101.  * integer (or, for a fixed point number - the standard argument - to
  3102.  * the nearest .00001).  Overflow and divide by zero are signalled in
  3103.  * the result, a boolean - true on success, false on overflow.
  3104.  */
  3105. int
  3106. png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
  3107.     png_int_32 divisor)
  3108. {
  3109.    /* Return a * times / divisor, rounded. */
  3110.    if (divisor != 0)
  3111.    {
  3112.       if (a == 0 || times == 0)
  3113.       {
  3114.          *res = 0;
  3115.          return 1;
  3116.       }
  3117.       else
  3118.       {
  3119. #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3120.          double r = a;
  3121.          r *= times;
  3122.          r /= divisor;
  3123.          r = floor(r+.5);
  3124.  
  3125.          /* A png_fixed_point is a 32-bit integer. */
  3126.          if (r <= 2147483647. && r >= -2147483648.)
  3127.          {
  3128.             *res = (png_fixed_point)r;
  3129.             return 1;
  3130.          }
  3131. #else
  3132.          int negative = 0;
  3133.          png_uint_32 A, T, D;
  3134.          png_uint_32 s16, s32, s00;
  3135.  
  3136.          if (a < 0)
  3137.             negative = 1, A = -a;
  3138.          else
  3139.             A = a;
  3140.  
  3141.          if (times < 0)
  3142.             negative = !negative, T = -times;
  3143.          else
  3144.             T = times;
  3145.  
  3146.          if (divisor < 0)
  3147.             negative = !negative, D = -divisor;
  3148.          else
  3149.             D = divisor;
  3150.  
  3151.          /* Following can't overflow because the arguments only
  3152.           * have 31 bits each, however the result may be 32 bits.
  3153.           */
  3154.          s16 = (A >> 16) * (T & 0xffff) +
  3155.                            (A & 0xffff) * (T >> 16);
  3156.          /* Can't overflow because the a*times bit is only 30
  3157.           * bits at most.
  3158.           */
  3159.          s32 = (A >> 16) * (T >> 16) + (s16 >> 16);
  3160.          s00 = (A & 0xffff) * (T & 0xffff);
  3161.  
  3162.          s16 = (s16 & 0xffff) << 16;
  3163.          s00 += s16;
  3164.  
  3165.          if (s00 < s16)
  3166.             ++s32; /* carry */
  3167.  
  3168.          if (s32 < D) /* else overflow */
  3169.          {
  3170.             /* s32.s00 is now the 64-bit product, do a standard
  3171.              * division, we know that s32 < D, so the maximum
  3172.              * required shift is 31.
  3173.              */
  3174.             int bitshift = 32;
  3175.             png_fixed_point result = 0; /* NOTE: signed */
  3176.  
  3177.             while (--bitshift >= 0)
  3178.             {
  3179.                png_uint_32 d32, d00;
  3180.  
  3181.                if (bitshift > 0)
  3182.                   d32 = D >> (32-bitshift), d00 = D << bitshift;
  3183.  
  3184.                else
  3185.                   d32 = 0, d00 = D;
  3186.  
  3187.                if (s32 > d32)
  3188.                {
  3189.                   if (s00 < d00) --s32; /* carry */
  3190.                   s32 -= d32, s00 -= d00, result += 1<<bitshift;
  3191.                }
  3192.  
  3193.                else
  3194.                   if (s32 == d32 && s00 >= d00)
  3195.                      s32 = 0, s00 -= d00, result += 1<<bitshift;
  3196.             }
  3197.  
  3198.             /* Handle the rounding. */
  3199.             if (s00 >= (D >> 1))
  3200.                ++result;
  3201.  
  3202.             if (negative)
  3203.                result = -result;
  3204.  
  3205.             /* Check for overflow. */
  3206.             if ((negative && result <= 0) || (!negative && result >= 0))
  3207.             {
  3208.                *res = result;
  3209.                return 1;
  3210.             }
  3211.          }
  3212. #endif
  3213.       }
  3214.    }
  3215.  
  3216.    return 0;
  3217. }
  3218. #endif /* READ_GAMMA || INCH_CONVERSIONS */
  3219.  
  3220. #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
  3221. /* The following is for when the caller doesn't much care about the
  3222.  * result.
  3223.  */
  3224. png_fixed_point
  3225. png_muldiv_warn(png_const_structrp png_ptr, png_fixed_point a, png_int_32 times,
  3226.     png_int_32 divisor)
  3227. {
  3228.    png_fixed_point result;
  3229.  
  3230.    if (png_muldiv(&result, a, times, divisor))
  3231.       return result;
  3232.  
  3233.    png_warning(png_ptr, "fixed point overflow ignored");
  3234.    return 0;
  3235. }
  3236. #endif
  3237.  
  3238. #ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */
  3239. /* Calculate a reciprocal, return 0 on div-by-zero or overflow. */
  3240. png_fixed_point
  3241. png_reciprocal(png_fixed_point a)
  3242. {
  3243. #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3244.    double r = floor(1E10/a+.5);
  3245.  
  3246.    if (r <= 2147483647. && r >= -2147483648.)
  3247.       return (png_fixed_point)r;
  3248. #else
  3249.    png_fixed_point res;
  3250.  
  3251.    if (png_muldiv(&res, 100000, 100000, a))
  3252.       return res;
  3253. #endif
  3254.  
  3255.    return 0; /* error/overflow */
  3256. }
  3257.  
  3258. /* This is the shared test on whether a gamma value is 'significant' - whether
  3259.  * it is worth doing gamma correction.
  3260.  */
  3261. int /* PRIVATE */
  3262. png_gamma_significant(png_fixed_point gamma_val)
  3263. {
  3264.    return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED ||
  3265.        gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED;
  3266. }
  3267. #endif
  3268.  
  3269. #ifdef PNG_READ_GAMMA_SUPPORTED
  3270. /* A local convenience routine. */
  3271. static png_fixed_point
  3272. png_product2(png_fixed_point a, png_fixed_point b)
  3273. {
  3274.    /* The required result is 1/a * 1/b; the following preserves accuracy. */
  3275. #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3276.    double r = a * 1E-5;
  3277.    r *= b;
  3278.    r = floor(r+.5);
  3279.  
  3280.    if (r <= 2147483647. && r >= -2147483648.)
  3281.       return (png_fixed_point)r;
  3282. #else
  3283.    png_fixed_point res;
  3284.  
  3285.    if (png_muldiv(&res, a, b, 100000))
  3286.       return res;
  3287. #endif
  3288.  
  3289.    return 0; /* overflow */
  3290. }
  3291.  
  3292. /* The inverse of the above. */
  3293. png_fixed_point
  3294. png_reciprocal2(png_fixed_point a, png_fixed_point b)
  3295. {
  3296.    /* The required result is 1/a * 1/b; the following preserves accuracy. */
  3297. #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3298.    double r = 1E15/a;
  3299.    r /= b;
  3300.    r = floor(r+.5);
  3301.  
  3302.    if (r <= 2147483647. && r >= -2147483648.)
  3303.       return (png_fixed_point)r;
  3304. #else
  3305.    /* This may overflow because the range of png_fixed_point isn't symmetric,
  3306.     * but this API is only used for the product of file and screen gamma so it
  3307.     * doesn't matter that the smallest number it can produce is 1/21474, not
  3308.     * 1/100000
  3309.     */
  3310.    png_fixed_point res = png_product2(a, b);
  3311.  
  3312.    if (res != 0)
  3313.       return png_reciprocal(res);
  3314. #endif
  3315.  
  3316.    return 0; /* overflow */
  3317. }
  3318. #endif /* READ_GAMMA */
  3319.  
  3320. #ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */
  3321. #ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3322. /* Fixed point gamma.
  3323.  *
  3324.  * The code to calculate the tables used below can be found in the shell script
  3325.  * contrib/tools/intgamma.sh
  3326.  *
  3327.  * To calculate gamma this code implements fast log() and exp() calls using only
  3328.  * fixed point arithmetic.  This code has sufficient precision for either 8-bit
  3329.  * or 16-bit sample values.
  3330.  *
  3331.  * The tables used here were calculated using simple 'bc' programs, but C double
  3332.  * precision floating point arithmetic would work fine.
  3333.  *
  3334.  * 8-bit log table
  3335.  *   This is a table of -log(value/255)/log(2) for 'value' in the range 128 to
  3336.  *   255, so it's the base 2 logarithm of a normalized 8-bit floating point
  3337.  *   mantissa.  The numbers are 32-bit fractions.
  3338.  */
  3339. static const png_uint_32
  3340. png_8bit_l2[128] =
  3341. {
  3342.    4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U,
  3343.    3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U,
  3344.    3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U,
  3345.    3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U,
  3346.    3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U,
  3347.    2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U,
  3348.    2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U,
  3349.    2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U,
  3350.    2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U,
  3351.    2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U,
  3352.    1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U,
  3353.    1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U,
  3354.    1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U,
  3355.    1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U,
  3356.    1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U,
  3357.    971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U,
  3358.    803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U,
  3359.    639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U,
  3360.    479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U,
  3361.    324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U,
  3362.    172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U,
  3363.    24347096U, 0U
  3364.  
  3365. #if 0
  3366.    /* The following are the values for 16-bit tables - these work fine for the
  3367.     * 8-bit conversions but produce very slightly larger errors in the 16-bit
  3368.     * log (about 1.2 as opposed to 0.7 absolute error in the final value).  To
  3369.     * use these all the shifts below must be adjusted appropriately.
  3370.     */
  3371.    65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054,
  3372.    57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803,
  3373.    50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068,
  3374.    43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782,
  3375.    37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887,
  3376.    31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339,
  3377.    25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098,
  3378.    20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132,
  3379.    15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415,
  3380.    10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523,
  3381.    6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495,
  3382.    1119, 744, 372
  3383. #endif
  3384. };
  3385.  
  3386. static png_int_32
  3387. png_log8bit(unsigned int x)
  3388. {
  3389.    unsigned int lg2 = 0;
  3390.    /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log,
  3391.     * because the log is actually negate that means adding 1.  The final
  3392.     * returned value thus has the range 0 (for 255 input) to 7.994 (for 1
  3393.     * input), return -1 for the overflow (log 0) case, - so the result is
  3394.     * always at most 19 bits.
  3395.     */
  3396.    if ((x &= 0xff) == 0)
  3397.       return -1;
  3398.  
  3399.    if ((x & 0xf0) == 0)
  3400.       lg2  = 4, x <<= 4;
  3401.  
  3402.    if ((x & 0xc0) == 0)
  3403.       lg2 += 2, x <<= 2;
  3404.  
  3405.    if ((x & 0x80) == 0)
  3406.       lg2 += 1, x <<= 1;
  3407.  
  3408.    /* result is at most 19 bits, so this cast is safe: */
  3409.    return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16));
  3410. }
  3411.  
  3412. /* The above gives exact (to 16 binary places) log2 values for 8-bit images,
  3413.  * for 16-bit images we use the most significant 8 bits of the 16-bit value to
  3414.  * get an approximation then multiply the approximation by a correction factor
  3415.  * determined by the remaining up to 8 bits.  This requires an additional step
  3416.  * in the 16-bit case.
  3417.  *
  3418.  * We want log2(value/65535), we have log2(v'/255), where:
  3419.  *
  3420.  *    value = v' * 256 + v''
  3421.  *          = v' * f
  3422.  *
  3423.  * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128
  3424.  * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less
  3425.  * than 258.  The final factor also needs to correct for the fact that our 8-bit
  3426.  * value is scaled by 255, whereas the 16-bit values must be scaled by 65535.
  3427.  *
  3428.  * This gives a final formula using a calculated value 'x' which is value/v' and
  3429.  * scaling by 65536 to match the above table:
  3430.  *
  3431.  *   log2(x/257) * 65536
  3432.  *
  3433.  * Since these numbers are so close to '1' we can use simple linear
  3434.  * interpolation between the two end values 256/257 (result -368.61) and 258/257
  3435.  * (result 367.179).  The values used below are scaled by a further 64 to give
  3436.  * 16-bit precision in the interpolation:
  3437.  *
  3438.  * Start (256): -23591
  3439.  * Zero  (257):      0
  3440.  * End   (258):  23499
  3441.  */
  3442. static png_int_32
  3443. png_log16bit(png_uint_32 x)
  3444. {
  3445.    unsigned int lg2 = 0;
  3446.  
  3447.    /* As above, but now the input has 16 bits. */
  3448.    if ((x &= 0xffff) == 0)
  3449.       return -1;
  3450.  
  3451.    if ((x & 0xff00) == 0)
  3452.       lg2  = 8, x <<= 8;
  3453.  
  3454.    if ((x & 0xf000) == 0)
  3455.       lg2 += 4, x <<= 4;
  3456.  
  3457.    if ((x & 0xc000) == 0)
  3458.       lg2 += 2, x <<= 2;
  3459.  
  3460.    if ((x & 0x8000) == 0)
  3461.       lg2 += 1, x <<= 1;
  3462.  
  3463.    /* Calculate the base logarithm from the top 8 bits as a 28-bit fractional
  3464.     * value.
  3465.     */
  3466.    lg2 <<= 28;
  3467.    lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4;
  3468.  
  3469.    /* Now we need to interpolate the factor, this requires a division by the top
  3470.     * 8 bits.  Do this with maximum precision.
  3471.     */
  3472.    x = ((x << 16) + (x >> 9)) / (x >> 8);
  3473.  
  3474.    /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24,
  3475.     * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly
  3476.     * 16 bits to interpolate to get the low bits of the result.  Round the
  3477.     * answer.  Note that the end point values are scaled by 64 to retain overall
  3478.     * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust
  3479.     * the overall scaling by 6-12.  Round at every step.
  3480.     */
  3481.    x -= 1U << 24;
  3482.  
  3483.    if (x <= 65536U) /* <= '257' */
  3484.       lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12);
  3485.  
  3486.    else
  3487.       lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12);
  3488.  
  3489.    /* Safe, because the result can't have more than 20 bits: */
  3490.    return (png_int_32)((lg2 + 2048) >> 12);
  3491. }
  3492.  
  3493. /* The 'exp()' case must invert the above, taking a 20-bit fixed point
  3494.  * logarithmic value and returning a 16 or 8-bit number as appropriate.  In
  3495.  * each case only the low 16 bits are relevant - the fraction - since the
  3496.  * integer bits (the top 4) simply determine a shift.
  3497.  *
  3498.  * The worst case is the 16-bit distinction between 65535 and 65534, this
  3499.  * requires perhaps spurious accuracty in the decoding of the logarithm to
  3500.  * distinguish log2(65535/65534.5) - 10^-5 or 17 bits.  There is little chance
  3501.  * of getting this accuracy in practice.
  3502.  *
  3503.  * To deal with this the following exp() function works out the exponent of the
  3504.  * frational part of the logarithm by using an accurate 32-bit value from the
  3505.  * top four fractional bits then multiplying in the remaining bits.
  3506.  */
  3507. static const png_uint_32
  3508. png_32bit_exp[16] =
  3509. {
  3510.    /* NOTE: the first entry is deliberately set to the maximum 32-bit value. */
  3511.    4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U,
  3512.    3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U,
  3513.    2553802834U, 2445529972U, 2341847524U, 2242560872U
  3514. };
  3515.  
  3516. /* Adjustment table; provided to explain the numbers in the code below. */
  3517. #if 0
  3518. for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"}
  3519.    11 44937.64284865548751208448
  3520.    10 45180.98734845585101160448
  3521.     9 45303.31936980687359311872
  3522.     8 45364.65110595323018870784
  3523.     7 45395.35850361789624614912
  3524.     6 45410.72259715102037508096
  3525.     5 45418.40724413220722311168
  3526.     4 45422.25021786898173001728
  3527.     3 45424.17186732298419044352
  3528.     2 45425.13273269940811464704
  3529.     1 45425.61317555035558641664
  3530.     0 45425.85339951654943850496
  3531. #endif
  3532.  
  3533. static png_uint_32
  3534. png_exp(png_fixed_point x)
  3535. {
  3536.    if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */
  3537.    {
  3538.       /* Obtain a 4-bit approximation */
  3539.       png_uint_32 e = png_32bit_exp[(x >> 12) & 0xf];
  3540.  
  3541.       /* Incorporate the low 12 bits - these decrease the returned value by
  3542.        * multiplying by a number less than 1 if the bit is set.  The multiplier
  3543.        * is determined by the above table and the shift. Notice that the values
  3544.        * converge on 45426 and this is used to allow linear interpolation of the
  3545.        * low bits.
  3546.        */
  3547.       if (x & 0x800)
  3548.          e -= (((e >> 16) * 44938U) +  16U) >> 5;
  3549.  
  3550.       if (x & 0x400)
  3551.          e -= (((e >> 16) * 45181U) +  32U) >> 6;
  3552.  
  3553.       if (x & 0x200)
  3554.          e -= (((e >> 16) * 45303U) +  64U) >> 7;
  3555.  
  3556.       if (x & 0x100)
  3557.          e -= (((e >> 16) * 45365U) + 128U) >> 8;
  3558.  
  3559.       if (x & 0x080)
  3560.          e -= (((e >> 16) * 45395U) + 256U) >> 9;
  3561.  
  3562.       if (x & 0x040)
  3563.          e -= (((e >> 16) * 45410U) + 512U) >> 10;
  3564.  
  3565.       /* And handle the low 6 bits in a single block. */
  3566.       e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9;
  3567.  
  3568.       /* Handle the upper bits of x. */
  3569.       e >>= x >> 16;
  3570.       return e;
  3571.    }
  3572.  
  3573.    /* Check for overflow */
  3574.    if (x <= 0)
  3575.       return png_32bit_exp[0];
  3576.  
  3577.    /* Else underflow */
  3578.    return 0;
  3579. }
  3580.  
  3581. static png_byte
  3582. png_exp8bit(png_fixed_point lg2)
  3583. {
  3584.    /* Get a 32-bit value: */
  3585.    png_uint_32 x = png_exp(lg2);
  3586.  
  3587.    /* Convert the 32-bit value to 0..255 by multiplying by 256-1, note that the
  3588.     * second, rounding, step can't overflow because of the first, subtraction,
  3589.     * step.
  3590.     */
  3591.    x -= x >> 8;
  3592.    return (png_byte)((x + 0x7fffffU) >> 24);
  3593. }
  3594.  
  3595. static png_uint_16
  3596. png_exp16bit(png_fixed_point lg2)
  3597. {
  3598.    /* Get a 32-bit value: */
  3599.    png_uint_32 x = png_exp(lg2);
  3600.  
  3601.    /* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */
  3602.    x -= x >> 16;
  3603.    return (png_uint_16)((x + 32767U) >> 16);
  3604. }
  3605. #endif /* FLOATING_ARITHMETIC */
  3606.  
  3607. png_byte
  3608. png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val)
  3609. {
  3610.    if (value > 0 && value < 255)
  3611.    {
  3612. #     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3613.          double r = floor(255*pow(value/255.,gamma_val*.00001)+.5);
  3614.          return (png_byte)r;
  3615. #     else
  3616.          png_int_32 lg2 = png_log8bit(value);
  3617.          png_fixed_point res;
  3618.  
  3619.          if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1))
  3620.             return png_exp8bit(res);
  3621.  
  3622.          /* Overflow. */
  3623.          value = 0;
  3624. #     endif
  3625.    }
  3626.  
  3627.    return (png_byte)value;
  3628. }
  3629.  
  3630. png_uint_16
  3631. png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val)
  3632. {
  3633.    if (value > 0 && value < 65535)
  3634.    {
  3635. #     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3636.          double r = floor(65535*pow(value/65535.,gamma_val*.00001)+.5);
  3637.          return (png_uint_16)r;
  3638. #     else
  3639.          png_int_32 lg2 = png_log16bit(value);
  3640.          png_fixed_point res;
  3641.  
  3642.          if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1))
  3643.             return png_exp16bit(res);
  3644.  
  3645.          /* Overflow. */
  3646.          value = 0;
  3647. #     endif
  3648.    }
  3649.  
  3650.    return (png_uint_16)value;
  3651. }
  3652.  
  3653. /* This does the right thing based on the bit_depth field of the
  3654.  * png_struct, interpreting values as 8-bit or 16-bit.  While the result
  3655.  * is nominally a 16-bit value if bit depth is 8 then the result is
  3656.  * 8-bit (as are the arguments.)
  3657.  */
  3658. png_uint_16 /* PRIVATE */
  3659. png_gamma_correct(png_structrp png_ptr, unsigned int value,
  3660.     png_fixed_point gamma_val)
  3661. {
  3662.    if (png_ptr->bit_depth == 8)
  3663.       return png_gamma_8bit_correct(value, gamma_val);
  3664.  
  3665.    else
  3666.       return png_gamma_16bit_correct(value, gamma_val);
  3667. }
  3668.  
  3669. /* Internal function to build a single 16-bit table - the table consists of
  3670.  * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount
  3671.  * to shift the input values right (or 16-number_of_signifiant_bits).
  3672.  *
  3673.  * The caller is responsible for ensuring that the table gets cleaned up on
  3674.  * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument
  3675.  * should be somewhere that will be cleaned.
  3676.  */
  3677. static void
  3678. png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
  3679.    PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
  3680. {
  3681.    /* Various values derived from 'shift': */
  3682.    PNG_CONST unsigned int num = 1U << (8U - shift);
  3683.    PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
  3684.    PNG_CONST unsigned int max_by_2 = 1U << (15U-shift);
  3685.    unsigned int i;
  3686.  
  3687.    png_uint_16pp table = *ptable =
  3688.        (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
  3689.  
  3690.    for (i = 0; i < num; i++)
  3691.    {
  3692.       png_uint_16p sub_table = table[i] =
  3693.           (png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16)));
  3694.  
  3695.       /* The 'threshold' test is repeated here because it can arise for one of
  3696.        * the 16-bit tables even if the others don't hit it.
  3697.        */
  3698.       if (png_gamma_significant(gamma_val))
  3699.       {
  3700.          /* The old code would overflow at the end and this would cause the
  3701.           * 'pow' function to return a result >1, resulting in an
  3702.           * arithmetic error.  This code follows the spec exactly; ig is
  3703.           * the recovered input sample, it always has 8-16 bits.
  3704.           *
  3705.           * We want input * 65535/max, rounded, the arithmetic fits in 32
  3706.           * bits (unsigned) so long as max <= 32767.
  3707.           */
  3708.          unsigned int j;
  3709.          for (j = 0; j < 256; j++)
  3710.          {
  3711.             png_uint_32 ig = (j << (8-shift)) + i;
  3712. #           ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
  3713.                /* Inline the 'max' scaling operation: */
  3714.                double d = floor(65535*pow(ig/(double)max, gamma_val*.00001)+.5);
  3715.                sub_table[j] = (png_uint_16)d;
  3716. #           else
  3717.                if (shift)
  3718.                   ig = (ig * 65535U + max_by_2)/max;
  3719.  
  3720.                sub_table[j] = png_gamma_16bit_correct(ig, gamma_val);
  3721. #           endif
  3722.          }
  3723.       }
  3724.       else
  3725.       {
  3726.          /* We must still build a table, but do it the fast way. */
  3727.          unsigned int j;
  3728.  
  3729.          for (j = 0; j < 256; j++)
  3730.          {
  3731.             png_uint_32 ig = (j << (8-shift)) + i;
  3732.  
  3733.             if (shift)
  3734.                ig = (ig * 65535U + max_by_2)/max;
  3735.  
  3736.             sub_table[j] = (png_uint_16)ig;
  3737.          }
  3738.       }
  3739.    }
  3740. }
  3741.  
  3742. /* NOTE: this function expects the *inverse* of the overall gamma transformation
  3743.  * required.
  3744.  */
  3745. static void
  3746. png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
  3747.    PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
  3748. {
  3749.    PNG_CONST unsigned int num = 1U << (8U - shift);
  3750.    PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
  3751.    unsigned int i;
  3752.    png_uint_32 last;
  3753.  
  3754.    png_uint_16pp table = *ptable =
  3755.        (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
  3756.  
  3757.    /* 'num' is the number of tables and also the number of low bits of low
  3758.     * bits of the input 16-bit value used to select a table.  Each table is
  3759.     * itself index by the high 8 bits of the value.
  3760.     */
  3761.    for (i = 0; i < num; i++)
  3762.       table[i] = (png_uint_16p)png_malloc(png_ptr,
  3763.           256 * (sizeof (png_uint_16)));
  3764.  
  3765.    /* 'gamma_val' is set to the reciprocal of the value calculated above, so
  3766.     * pow(out,g) is an *input* value.  'last' is the last input value set.
  3767.     *
  3768.     * In the loop 'i' is used to find output values.  Since the output is
  3769.     * 8-bit there are only 256 possible values.  The tables are set up to
  3770.     * select the closest possible output value for each input by finding
  3771.     * the input value at the boundary between each pair of output values
  3772.     * and filling the table up to that boundary with the lower output
  3773.     * value.
  3774.     *
  3775.     * The boundary values are 0.5,1.5..253.5,254.5.  Since these are 9-bit
  3776.     * values the code below uses a 16-bit value in i; the values start at
  3777.     * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last
  3778.     * entries are filled with 255).  Start i at 128 and fill all 'last'
  3779.     * table entries <= 'max'
  3780.     */
  3781.    last = 0;
  3782.    for (i = 0; i < 255; ++i) /* 8-bit output value */
  3783.    {
  3784.       /* Find the corresponding maximum input value */
  3785.       png_uint_16 out = (png_uint_16)(i * 257U); /* 16-bit output value */
  3786.  
  3787.       /* Find the boundary value in 16 bits: */
  3788.       png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val);
  3789.  
  3790.       /* Adjust (round) to (16-shift) bits: */
  3791.       bound = (bound * max + 32768U)/65535U + 1U;
  3792.  
  3793.       while (last < bound)
  3794.       {
  3795.          table[last & (0xffU >> shift)][last >> (8U - shift)] = out;
  3796.          last++;
  3797.       }
  3798.    }
  3799.  
  3800.    /* And fill in the final entries. */
  3801.    while (last < (num << 8))
  3802.    {
  3803.       table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U;
  3804.       last++;
  3805.    }
  3806. }
  3807.  
  3808. /* Build a single 8-bit table: same as the 16-bit case but much simpler (and
  3809.  * typically much faster).  Note that libpng currently does no sBIT processing
  3810.  * (apparently contrary to the spec) so a 256 entry table is always generated.
  3811.  */
  3812. static void
  3813. png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
  3814.    PNG_CONST png_fixed_point gamma_val)
  3815. {
  3816.    unsigned int i;
  3817.    png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256);
  3818.  
  3819.    if (png_gamma_significant(gamma_val)) for (i=0; i<256; i++)
  3820.       table[i] = png_gamma_8bit_correct(i, gamma_val);
  3821.  
  3822.    else for (i=0; i<256; ++i)
  3823.       table[i] = (png_byte)i;
  3824. }
  3825.  
  3826. /* Used from png_read_destroy and below to release the memory used by the gamma
  3827.  * tables.
  3828.  */
  3829. void /* PRIVATE */
  3830. png_destroy_gamma_table(png_structrp png_ptr)
  3831. {
  3832.    png_free(png_ptr, png_ptr->gamma_table);
  3833.    png_ptr->gamma_table = NULL;
  3834.  
  3835.    if (png_ptr->gamma_16_table != NULL)
  3836.    {
  3837.       int i;
  3838.       int istop = (1 << (8 - png_ptr->gamma_shift));
  3839.       for (i = 0; i < istop; i++)
  3840.       {
  3841.          png_free(png_ptr, png_ptr->gamma_16_table[i]);
  3842.       }
  3843.    png_free(png_ptr, png_ptr->gamma_16_table);
  3844.    png_ptr->gamma_16_table = NULL;
  3845.    }
  3846.  
  3847. #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
  3848.    defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
  3849.    defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
  3850.    png_free(png_ptr, png_ptr->gamma_from_1);
  3851.    png_ptr->gamma_from_1 = NULL;
  3852.    png_free(png_ptr, png_ptr->gamma_to_1);
  3853.    png_ptr->gamma_to_1 = NULL;
  3854.  
  3855.    if (png_ptr->gamma_16_from_1 != NULL)
  3856.    {
  3857.       int i;
  3858.       int istop = (1 << (8 - png_ptr->gamma_shift));
  3859.       for (i = 0; i < istop; i++)
  3860.       {
  3861.          png_free(png_ptr, png_ptr->gamma_16_from_1[i]);
  3862.       }
  3863.    png_free(png_ptr, png_ptr->gamma_16_from_1);
  3864.    png_ptr->gamma_16_from_1 = NULL;
  3865.    }
  3866.    if (png_ptr->gamma_16_to_1 != NULL)
  3867.    {
  3868.       int i;
  3869.       int istop = (1 << (8 - png_ptr->gamma_shift));
  3870.       for (i = 0; i < istop; i++)
  3871.       {
  3872.          png_free(png_ptr, png_ptr->gamma_16_to_1[i]);
  3873.       }
  3874.    png_free(png_ptr, png_ptr->gamma_16_to_1);
  3875.    png_ptr->gamma_16_to_1 = NULL;
  3876.    }
  3877. #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
  3878. }
  3879.  
  3880. /* We build the 8- or 16-bit gamma tables here.  Note that for 16-bit
  3881.  * tables, we don't make a full table if we are reducing to 8-bit in
  3882.  * the future.  Note also how the gamma_16 tables are segmented so that
  3883.  * we don't need to allocate > 64K chunks for a full 16-bit table.
  3884.  */
  3885. void /* PRIVATE */
  3886. png_build_gamma_table(png_structrp png_ptr, int bit_depth)
  3887. {
  3888.   png_debug(1, "in png_build_gamma_table");
  3889.  
  3890.   /* Remove any existing table; this copes with multiple calls to
  3891.    * png_read_update_info.  The warning is because building the gamma tables
  3892.    * multiple times is a performance hit - it's harmless but the ability to call
  3893.    * png_read_update_info() multiple times is new in 1.5.6 so it seems sensible
  3894.    * to warn if the app introduces such a hit.
  3895.    */
  3896.   if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)
  3897.   {
  3898.     png_warning(png_ptr, "gamma table being rebuilt");
  3899.     png_destroy_gamma_table(png_ptr);
  3900.   }
  3901.  
  3902.   if (bit_depth <= 8)
  3903.   {
  3904.      png_build_8bit_table(png_ptr, &png_ptr->gamma_table,
  3905.          png_ptr->screen_gamma > 0 ?  png_reciprocal2(png_ptr->colorspace.gamma,
  3906.          png_ptr->screen_gamma) : PNG_FP_1);
  3907.  
  3908. #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
  3909.    defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
  3910.    defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
  3911.      if (png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY))
  3912.      {
  3913.         png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1,
  3914.             png_reciprocal(png_ptr->colorspace.gamma));
  3915.  
  3916.         png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1,
  3917.             png_ptr->screen_gamma > 0 ?  png_reciprocal(png_ptr->screen_gamma) :
  3918.             png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
  3919.      }
  3920. #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
  3921.   }
  3922.   else
  3923.   {
  3924.      png_byte shift, sig_bit;
  3925.  
  3926.      if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
  3927.      {
  3928.         sig_bit = png_ptr->sig_bit.red;
  3929.  
  3930.         if (png_ptr->sig_bit.green > sig_bit)
  3931.            sig_bit = png_ptr->sig_bit.green;
  3932.  
  3933.         if (png_ptr->sig_bit.blue > sig_bit)
  3934.            sig_bit = png_ptr->sig_bit.blue;
  3935.      }
  3936.      else
  3937.         sig_bit = png_ptr->sig_bit.gray;
  3938.  
  3939.      /* 16-bit gamma code uses this equation:
  3940.       *
  3941.       *   ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
  3942.       *
  3943.       * Where 'iv' is the input color value and 'ov' is the output value -
  3944.       * pow(iv, gamma).
  3945.       *
  3946.       * Thus the gamma table consists of up to 256 256 entry tables.  The table
  3947.       * is selected by the (8-gamma_shift) most significant of the low 8 bits of
  3948.       * the color value then indexed by the upper 8 bits:
  3949.       *
  3950.       *   table[low bits][high 8 bits]
  3951.       *
  3952.       * So the table 'n' corresponds to all those 'iv' of:
  3953.       *
  3954.       *   <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
  3955.       *
  3956.       */
  3957.      if (sig_bit > 0 && sig_bit < 16U)
  3958.         shift = (png_byte)(16U - sig_bit); /* shift == insignificant bits */
  3959.  
  3960.      else
  3961.         shift = 0; /* keep all 16 bits */
  3962.  
  3963.      if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))
  3964.      {
  3965.         /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
  3966.          * the significant bits in the *input* when the output will
  3967.          * eventually be 8 bits.  By default it is 11.
  3968.          */
  3969.         if (shift < (16U - PNG_MAX_GAMMA_8))
  3970.            shift = (16U - PNG_MAX_GAMMA_8);
  3971.      }
  3972.  
  3973.      if (shift > 8U)
  3974.         shift = 8U; /* Guarantees at least one table! */
  3975.  
  3976.      png_ptr->gamma_shift = shift;
  3977.  
  3978. #ifdef PNG_16BIT_SUPPORTED
  3979.      /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
  3980.       * PNG_COMPOSE).  This effectively smashed the background calculation for
  3981.       * 16-bit output because the 8-bit table assumes the result will be reduced
  3982.       * to 8 bits.
  3983.       */
  3984.      if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))
  3985. #endif
  3986.          png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
  3987.          png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
  3988.          png_ptr->screen_gamma) : PNG_FP_1);
  3989.  
  3990. #ifdef PNG_16BIT_SUPPORTED
  3991.      else
  3992.          png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
  3993.          png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,
  3994.          png_ptr->screen_gamma) : PNG_FP_1);
  3995. #endif
  3996.  
  3997. #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
  3998.    defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
  3999.    defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
  4000.      if (png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY))
  4001.      {
  4002.         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift,
  4003.             png_reciprocal(png_ptr->colorspace.gamma));
  4004.  
  4005.         /* Notice that the '16 from 1' table should be full precision, however
  4006.          * the lookup on this table still uses gamma_shift, so it can't be.
  4007.          * TODO: fix this.
  4008.          */
  4009.         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,
  4010.             png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) :
  4011.             png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
  4012.      }
  4013. #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
  4014.   }
  4015. }
  4016. #endif /* READ_GAMMA */
  4017.  
  4018. /* HARDWARE OPTION SUPPORT */
  4019. #ifdef PNG_SET_OPTION_SUPPORTED
  4020. int PNGAPI
  4021. png_set_option(png_structrp png_ptr, int option, int onoff)
  4022. {
  4023.    if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT &&
  4024.       (option & 1) == 0)
  4025.    {
  4026.       int mask = 3 << option;
  4027.       int setting = (2 + (onoff != 0)) << option;
  4028.       int current = png_ptr->options;
  4029.  
  4030.       png_ptr->options = (png_byte)((current & ~mask) | setting);
  4031.  
  4032.       return (current & mask) >> option;
  4033.    }
  4034.  
  4035.    return PNG_OPTION_INVALID;
  4036. }
  4037. #endif
  4038.  
  4039. /* sRGB support */
  4040. #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
  4041.    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  4042. /* sRGB conversion tables; these are machine generated with the code in
  4043.  * contrib/tools/makesRGB.c.  The actual sRGB transfer curve defined in the
  4044.  * specification (see the article at http://en.wikipedia.org/wiki/SRGB)
  4045.  * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.
  4046.  * The sRGB to linear table is exact (to the nearest 16 bit linear fraction).
  4047.  * The inverse (linear to sRGB) table has accuracies as follows:
  4048.  *
  4049.  * For all possible (255*65535+1) input values:
  4050.  *
  4051.  *    error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact
  4052.  *
  4053.  * For the input values corresponding to the 65536 16-bit values:
  4054.  *
  4055.  *    error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact
  4056.  *
  4057.  * In all cases the inexact readings are off by one.
  4058.  */
  4059.  
  4060. #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
  4061. /* The convert-to-sRGB table is only currently required for read. */
  4062. const png_uint_16 png_sRGB_table[256] =
  4063. {
  4064.    0,20,40,60,80,99,119,139,
  4065.    159,179,199,219,241,264,288,313,
  4066.    340,367,396,427,458,491,526,562,
  4067.    599,637,677,718,761,805,851,898,
  4068.    947,997,1048,1101,1156,1212,1270,1330,
  4069.    1391,1453,1517,1583,1651,1720,1790,1863,
  4070.    1937,2013,2090,2170,2250,2333,2418,2504,
  4071.    2592,2681,2773,2866,2961,3058,3157,3258,
  4072.    3360,3464,3570,3678,3788,3900,4014,4129,
  4073.    4247,4366,4488,4611,4736,4864,4993,5124,
  4074.    5257,5392,5530,5669,5810,5953,6099,6246,
  4075.    6395,6547,6700,6856,7014,7174,7335,7500,
  4076.    7666,7834,8004,8177,8352,8528,8708,8889,
  4077.    9072,9258,9445,9635,9828,10022,10219,10417,
  4078.    10619,10822,11028,11235,11446,11658,11873,12090,
  4079.    12309,12530,12754,12980,13209,13440,13673,13909,
  4080.    14146,14387,14629,14874,15122,15371,15623,15878,
  4081.    16135,16394,16656,16920,17187,17456,17727,18001,
  4082.    18277,18556,18837,19121,19407,19696,19987,20281,
  4083.    20577,20876,21177,21481,21787,22096,22407,22721,
  4084.    23038,23357,23678,24002,24329,24658,24990,25325,
  4085.    25662,26001,26344,26688,27036,27386,27739,28094,
  4086.    28452,28813,29176,29542,29911,30282,30656,31033,
  4087.    31412,31794,32179,32567,32957,33350,33745,34143,
  4088.    34544,34948,35355,35764,36176,36591,37008,37429,
  4089.    37852,38278,38706,39138,39572,40009,40449,40891,
  4090.    41337,41785,42236,42690,43147,43606,44069,44534,
  4091.    45002,45473,45947,46423,46903,47385,47871,48359,
  4092.    48850,49344,49841,50341,50844,51349,51858,52369,
  4093.    52884,53401,53921,54445,54971,55500,56032,56567,
  4094.    57105,57646,58190,58737,59287,59840,60396,60955,
  4095.    61517,62082,62650,63221,63795,64372,64952,65535
  4096. };
  4097.  
  4098. #endif /* simplified read only */
  4099.  
  4100. /* The base/delta tables are required for both read and write (but currently
  4101.  * only the simplified versions.)
  4102.  */
  4103. const png_uint_16 png_sRGB_base[512] =
  4104. {
  4105.    128,1782,3383,4644,5675,6564,7357,8074,
  4106.    8732,9346,9921,10463,10977,11466,11935,12384,
  4107.    12816,13233,13634,14024,14402,14769,15125,15473,
  4108.    15812,16142,16466,16781,17090,17393,17690,17981,
  4109.    18266,18546,18822,19093,19359,19621,19879,20133,
  4110.    20383,20630,20873,21113,21349,21583,21813,22041,
  4111.    22265,22487,22707,22923,23138,23350,23559,23767,
  4112.    23972,24175,24376,24575,24772,24967,25160,25352,
  4113.    25542,25730,25916,26101,26284,26465,26645,26823,
  4114.    27000,27176,27350,27523,27695,27865,28034,28201,
  4115.    28368,28533,28697,28860,29021,29182,29341,29500,
  4116.    29657,29813,29969,30123,30276,30429,30580,30730,
  4117.    30880,31028,31176,31323,31469,31614,31758,31902,
  4118.    32045,32186,32327,32468,32607,32746,32884,33021,
  4119.    33158,33294,33429,33564,33697,33831,33963,34095,
  4120.    34226,34357,34486,34616,34744,34873,35000,35127,
  4121.    35253,35379,35504,35629,35753,35876,35999,36122,
  4122.    36244,36365,36486,36606,36726,36845,36964,37083,
  4123.    37201,37318,37435,37551,37668,37783,37898,38013,
  4124.    38127,38241,38354,38467,38580,38692,38803,38915,
  4125.    39026,39136,39246,39356,39465,39574,39682,39790,
  4126.    39898,40005,40112,40219,40325,40431,40537,40642,
  4127.    40747,40851,40955,41059,41163,41266,41369,41471,
  4128.    41573,41675,41777,41878,41979,42079,42179,42279,
  4129.    42379,42478,42577,42676,42775,42873,42971,43068,
  4130.    43165,43262,43359,43456,43552,43648,43743,43839,
  4131.    43934,44028,44123,44217,44311,44405,44499,44592,
  4132.    44685,44778,44870,44962,45054,45146,45238,45329,
  4133.    45420,45511,45601,45692,45782,45872,45961,46051,
  4134.    46140,46229,46318,46406,46494,46583,46670,46758,
  4135.    46846,46933,47020,47107,47193,47280,47366,47452,
  4136.    47538,47623,47709,47794,47879,47964,48048,48133,
  4137.    48217,48301,48385,48468,48552,48635,48718,48801,
  4138.    48884,48966,49048,49131,49213,49294,49376,49458,
  4139.    49539,49620,49701,49782,49862,49943,50023,50103,
  4140.    50183,50263,50342,50422,50501,50580,50659,50738,
  4141.    50816,50895,50973,51051,51129,51207,51285,51362,
  4142.    51439,51517,51594,51671,51747,51824,51900,51977,
  4143.    52053,52129,52205,52280,52356,52432,52507,52582,
  4144.    52657,52732,52807,52881,52956,53030,53104,53178,
  4145.    53252,53326,53400,53473,53546,53620,53693,53766,
  4146.    53839,53911,53984,54056,54129,54201,54273,54345,
  4147.    54417,54489,54560,54632,54703,54774,54845,54916,
  4148.    54987,55058,55129,55199,55269,55340,55410,55480,
  4149.    55550,55620,55689,55759,55828,55898,55967,56036,
  4150.    56105,56174,56243,56311,56380,56448,56517,56585,
  4151.    56653,56721,56789,56857,56924,56992,57059,57127,
  4152.    57194,57261,57328,57395,57462,57529,57595,57662,
  4153.    57728,57795,57861,57927,57993,58059,58125,58191,
  4154.    58256,58322,58387,58453,58518,58583,58648,58713,
  4155.    58778,58843,58908,58972,59037,59101,59165,59230,
  4156.    59294,59358,59422,59486,59549,59613,59677,59740,
  4157.    59804,59867,59930,59993,60056,60119,60182,60245,
  4158.    60308,60370,60433,60495,60558,60620,60682,60744,
  4159.    60806,60868,60930,60992,61054,61115,61177,61238,
  4160.    61300,61361,61422,61483,61544,61605,61666,61727,
  4161.    61788,61848,61909,61969,62030,62090,62150,62211,
  4162.    62271,62331,62391,62450,62510,62570,62630,62689,
  4163.    62749,62808,62867,62927,62986,63045,63104,63163,
  4164.    63222,63281,63340,63398,63457,63515,63574,63632,
  4165.    63691,63749,63807,63865,63923,63981,64039,64097,
  4166.    64155,64212,64270,64328,64385,64443,64500,64557,
  4167.    64614,64672,64729,64786,64843,64900,64956,65013,
  4168.    65070,65126,65183,65239,65296,65352,65409,65465
  4169. };
  4170.  
  4171. const png_byte png_sRGB_delta[512] =
  4172. {
  4173.    207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54,
  4174.    52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36,
  4175.    35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28,
  4176.    28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24,
  4177.    23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21,
  4178.    21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19,
  4179.    19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17,
  4180.    17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16,
  4181.    16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15,
  4182.    15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14,
  4183.    14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13,
  4184.    13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12,
  4185.    12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,
  4186.    12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11,
  4187.    11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
  4188.    11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
  4189.    11,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  4190.    10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  4191.    10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  4192.    10,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
  4193.    9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
  4194.    9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
  4195.    9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
  4196.    9,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
  4197.    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
  4198.    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
  4199.    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
  4200.    8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
  4201.    8,8,8,8,8,8,8,8,8,7,7,7,7,7,7,7,
  4202.    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  4203.    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  4204.    7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
  4205. };
  4206. #endif /* SIMPLIFIED READ/WRITE sRGB support */
  4207.  
  4208. /* SIMPLIFIED READ/WRITE SUPPORT */
  4209. #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
  4210.    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  4211. static int
  4212. png_image_free_function(png_voidp argument)
  4213. {
  4214.    png_imagep image = png_voidcast(png_imagep, argument);
  4215.    png_controlp cp = image->opaque;
  4216.    png_control c;
  4217.  
  4218.    /* Double check that we have a png_ptr - it should be impossible to get here
  4219.     * without one.
  4220.     */
  4221.    if (cp->png_ptr == NULL)
  4222.       return 0;
  4223.  
  4224.    /* First free any data held in the control structure. */
  4225. #  ifdef PNG_STDIO_SUPPORTED
  4226.       if (cp->owned_file)
  4227.       {
  4228.          FILE *fp = png_voidcast(FILE*, cp->png_ptr->io_ptr);
  4229.          cp->owned_file = 0;
  4230.  
  4231.          /* Ignore errors here. */
  4232.          if (fp != NULL)
  4233.          {
  4234.             cp->png_ptr->io_ptr = NULL;
  4235.             (void)fclose(fp);
  4236.          }
  4237.       }
  4238. #  endif
  4239.  
  4240.    /* Copy the control structure so that the original, allocated, version can be
  4241.     * safely freed.  Notice that a png_error here stops the remainder of the
  4242.     * cleanup, but this is probably fine because that would indicate bad memory
  4243.     * problems anyway.
  4244.     */
  4245.    c = *cp;
  4246.    image->opaque = &c;
  4247.    png_free(c.png_ptr, cp);
  4248.  
  4249.    /* Then the structures, calling the correct API. */
  4250.    if (c.for_write)
  4251.    {
  4252. #     ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
  4253.          png_destroy_write_struct(&c.png_ptr, &c.info_ptr);
  4254. #     else
  4255.          png_error(c.png_ptr, "simplified write not supported");
  4256. #     endif
  4257.    }
  4258.    else
  4259.    {
  4260. #     ifdef PNG_SIMPLIFIED_READ_SUPPORTED
  4261.          png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL);
  4262. #     else
  4263.          png_error(c.png_ptr, "simplified read not supported");
  4264. #     endif
  4265.    }
  4266.  
  4267.    /* Success. */
  4268.    return 1;
  4269. }
  4270.  
  4271. void PNGAPI
  4272. png_image_free(png_imagep image)
  4273. {
  4274.    /* Safely call the real function, but only if doing so is safe at this point
  4275.     * (if not inside an error handling context).  Otherwise assume
  4276.     * png_safe_execute will call this API after the return.
  4277.     */
  4278.    if (image != NULL && image->opaque != NULL &&
  4279.       image->opaque->error_buf == NULL)
  4280.    {
  4281.       /* Ignore errors here: */
  4282.       (void)png_safe_execute(image, png_image_free_function, image);
  4283.       image->opaque = NULL;
  4284.    }
  4285. }
  4286.  
  4287. int /* PRIVATE */
  4288. png_image_error(png_imagep image, png_const_charp error_message)
  4289. {
  4290.    /* Utility to log an error. */
  4291.    png_safecat(image->message, (sizeof image->message), 0, error_message);
  4292.    image->warning_or_error |= PNG_IMAGE_ERROR;
  4293.    png_image_free(image);
  4294.    return 0;
  4295. }
  4296.  
  4297. #endif /* SIMPLIFIED READ/WRITE */
  4298. #endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
  4299.