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  1.  
  2. /* pngwutil.c - utilities to write a PNG file
  3.  *
  4.  * Last changed in libpng 1.5.0 [January 6, 2011]
  5.  * Copyright (c) 1998-2011 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. #ifdef PNG_WRITE_SUPPORTED
  17.  
  18. #ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
  19. /* Place a 32-bit number into a buffer in PNG byte order.  We work
  20.  * with unsigned numbers for convenience, although one supported
  21.  * ancillary chunk uses signed (two's complement) numbers.
  22.  */
  23. void PNGAPI
  24. png_save_uint_32(png_bytep buf, png_uint_32 i)
  25. {
  26.    buf[0] = (png_byte)((i >> 24) & 0xff);
  27.    buf[1] = (png_byte)((i >> 16) & 0xff);
  28.    buf[2] = (png_byte)((i >> 8) & 0xff);
  29.    buf[3] = (png_byte)(i & 0xff);
  30. }
  31.  
  32. #ifdef PNG_SAVE_INT_32_SUPPORTED
  33. /* The png_save_int_32 function assumes integers are stored in two's
  34.  * complement format.  If this isn't the case, then this routine needs to
  35.  * be modified to write data in two's complement format.  Note that,
  36.  * the following works correctly even if png_int_32 has more than 32 bits
  37.  * (compare the more complex code required on read for sign extention.)
  38.  */
  39. void PNGAPI
  40. png_save_int_32(png_bytep buf, png_int_32 i)
  41. {
  42.    buf[0] = (png_byte)((i >> 24) & 0xff);
  43.    buf[1] = (png_byte)((i >> 16) & 0xff);
  44.    buf[2] = (png_byte)((i >> 8) & 0xff);
  45.    buf[3] = (png_byte)(i & 0xff);
  46. }
  47. #endif
  48.  
  49. /* Place a 16-bit number into a buffer in PNG byte order.
  50.  * The parameter is declared unsigned int, not png_uint_16,
  51.  * just to avoid potential problems on pre-ANSI C compilers.
  52.  */
  53. void PNGAPI
  54. png_save_uint_16(png_bytep buf, unsigned int i)
  55. {
  56.    buf[0] = (png_byte)((i >> 8) & 0xff);
  57.    buf[1] = (png_byte)(i & 0xff);
  58. }
  59. #endif
  60.  
  61. /* Simple function to write the signature.  If we have already written
  62.  * the magic bytes of the signature, or more likely, the PNG stream is
  63.  * being embedded into another stream and doesn't need its own signature,
  64.  * we should call png_set_sig_bytes() to tell libpng how many of the
  65.  * bytes have already been written.
  66.  */
  67. void PNGAPI
  68. png_write_sig(png_structp png_ptr)
  69. {
  70.    png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  71.  
  72. #ifdef PNG_IO_STATE_SUPPORTED
  73.    /* Inform the I/O callback that the signature is being written */
  74.    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_SIGNATURE;
  75. #endif
  76.  
  77.    /* Write the rest of the 8 byte signature */
  78.    png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
  79.       (png_size_t)(8 - png_ptr->sig_bytes));
  80.  
  81.    if (png_ptr->sig_bytes < 3)
  82.       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
  83. }
  84.  
  85. /* Write a PNG chunk all at once.  The type is an array of ASCII characters
  86.  * representing the chunk name.  The array must be at least 4 bytes in
  87.  * length, and does not need to be null terminated.  To be safe, pass the
  88.  * pre-defined chunk names here, and if you need a new one, define it
  89.  * where the others are defined.  The length is the length of the data.
  90.  * All the data must be present.  If that is not possible, use the
  91.  * png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
  92.  * functions instead.
  93.  */
  94. void PNGAPI
  95. png_write_chunk(png_structp png_ptr, png_const_bytep chunk_name,
  96.    png_const_bytep data, png_size_t length)
  97. {
  98.    if (png_ptr == NULL)
  99.       return;
  100.  
  101.    png_write_chunk_start(png_ptr, chunk_name, (png_uint_32)length);
  102.    png_write_chunk_data(png_ptr, data, (png_size_t)length);
  103.    png_write_chunk_end(png_ptr);
  104. }
  105.  
  106. /* Write the start of a PNG chunk.  The type is the chunk type.
  107.  * The total_length is the sum of the lengths of all the data you will be
  108.  * passing in png_write_chunk_data().
  109.  */
  110. void PNGAPI
  111. png_write_chunk_start(png_structp png_ptr, png_const_bytep chunk_name,
  112.     png_uint_32 length)
  113. {
  114.    png_byte buf[8];
  115.  
  116.    png_debug2(0, "Writing %s chunk, length = %lu", chunk_name,
  117.       (unsigned long)length);
  118.  
  119.    if (png_ptr == NULL)
  120.       return;
  121.  
  122. #ifdef PNG_IO_STATE_SUPPORTED
  123.    /* Inform the I/O callback that the chunk header is being written.
  124.     * PNG_IO_CHUNK_HDR requires a single I/O call.
  125.     */
  126.    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_HDR;
  127. #endif
  128.  
  129.    /* Write the length and the chunk name */
  130.    png_save_uint_32(buf, length);
  131.    png_memcpy(buf + 4, chunk_name, 4);
  132.    png_write_data(png_ptr, buf, (png_size_t)8);
  133.  
  134.    /* Put the chunk name into png_ptr->chunk_name */
  135.    png_memcpy(png_ptr->chunk_name, chunk_name, 4);
  136.  
  137.    /* Reset the crc and run it over the chunk name */
  138.    png_reset_crc(png_ptr);
  139.  
  140.    png_calculate_crc(png_ptr, chunk_name, 4);
  141.  
  142. #ifdef PNG_IO_STATE_SUPPORTED
  143.    /* Inform the I/O callback that chunk data will (possibly) be written.
  144.     * PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
  145.     */
  146.    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_DATA;
  147. #endif
  148. }
  149.  
  150. /* Write the data of a PNG chunk started with png_write_chunk_start().
  151.  * Note that multiple calls to this function are allowed, and that the
  152.  * sum of the lengths from these calls *must* add up to the total_length
  153.  * given to png_write_chunk_start().
  154.  */
  155. void PNGAPI
  156. png_write_chunk_data(png_structp png_ptr, png_const_bytep data,
  157.     png_size_t length)
  158. {
  159.    /* Write the data, and run the CRC over it */
  160.    if (png_ptr == NULL)
  161.       return;
  162.  
  163.    if (data != NULL && length > 0)
  164.    {
  165.       png_write_data(png_ptr, data, length);
  166.  
  167.       /* Update the CRC after writing the data,
  168.        * in case that the user I/O routine alters it.
  169.        */
  170.       png_calculate_crc(png_ptr, data, length);
  171.    }
  172. }
  173.  
  174. /* Finish a chunk started with png_write_chunk_start(). */
  175. void PNGAPI
  176. png_write_chunk_end(png_structp png_ptr)
  177. {
  178.    png_byte buf[4];
  179.  
  180.    if (png_ptr == NULL) return;
  181.  
  182. #ifdef PNG_IO_STATE_SUPPORTED
  183.    /* Inform the I/O callback that the chunk CRC is being written.
  184.     * PNG_IO_CHUNK_CRC requires a single I/O function call.
  185.     */
  186.    png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_CRC;
  187. #endif
  188.  
  189.    /* Write the crc in a single operation */
  190.    png_save_uint_32(buf, png_ptr->crc);
  191.  
  192.    png_write_data(png_ptr, buf, (png_size_t)4);
  193. }
  194.  
  195. #if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_iCCP_SUPPORTED)
  196. /* This pair of functions encapsulates the operation of (a) compressing a
  197.  * text string, and (b) issuing it later as a series of chunk data writes.
  198.  * The compression_state structure is shared context for these functions
  199.  * set up by the caller in order to make the whole mess thread-safe.
  200.  */
  201.  
  202. typedef struct
  203. {
  204.    png_const_bytep input;   /* The uncompressed input data */
  205.    png_size_t input_len;    /* Its length */
  206.    int num_output_ptr;      /* Number of output pointers used */
  207.    int max_output_ptr;      /* Size of output_ptr */
  208.    png_bytep *output_ptr;   /* Array of pointers to output */
  209. } compression_state;
  210.  
  211. /* Compress given text into storage in the png_ptr structure */
  212. static int /* PRIVATE */
  213. png_text_compress(png_structp png_ptr,
  214.     png_const_charp text, png_size_t text_len, int compression,
  215.     compression_state *comp)
  216. {
  217.    int ret;
  218.  
  219.    comp->num_output_ptr = 0;
  220.    comp->max_output_ptr = 0;
  221.    comp->output_ptr = NULL;
  222.    comp->input = NULL;
  223.    comp->input_len = 0;
  224.  
  225.    /* We may just want to pass the text right through */
  226.    if (compression == PNG_TEXT_COMPRESSION_NONE)
  227.    {
  228.       comp->input = (png_const_bytep)text;
  229.       comp->input_len = text_len;
  230.       return((int)text_len);
  231.    }
  232.  
  233.    if (compression >= PNG_TEXT_COMPRESSION_LAST)
  234.    {
  235. #ifdef PNG_CONSOLE_IO_SUPPORTED
  236.       char msg[50];
  237.       png_snprintf(msg, 50, "Unknown compression type %d", compression);
  238.       png_warning(png_ptr, msg);
  239. #else
  240.       png_warning(png_ptr, "Unknown compression type");
  241. #endif
  242.    }
  243.  
  244.    /* We can't write the chunk until we find out how much data we have,
  245.     * which means we need to run the compressor first and save the
  246.     * output.  This shouldn't be a problem, as the vast majority of
  247.     * comments should be reasonable, but we will set up an array of
  248.     * malloc'd pointers to be sure.
  249.     *
  250.     * If we knew the application was well behaved, we could simplify this
  251.     * greatly by assuming we can always malloc an output buffer large
  252.     * enough to hold the compressed text ((1001 * text_len / 1000) + 12)
  253.     * and malloc this directly.  The only time this would be a bad idea is
  254.     * if we can't malloc more than 64K and we have 64K of random input
  255.     * data, or if the input string is incredibly large (although this
  256.     * wouldn't cause a failure, just a slowdown due to swapping).
  257.     */
  258.  
  259.    /* Set up the compression buffers */
  260.    /* TODO: the following cast hides a potential overflow problem. */
  261.    png_ptr->zstream.avail_in = (uInt)text_len;
  262.    /* NOTE: assume zlib doesn't overwrite the input */
  263.    png_ptr->zstream.next_in = (Bytef *)text;
  264.    png_ptr->zstream.avail_out = png_ptr->zbuf_size;
  265.    png_ptr->zstream.next_out = png_ptr->zbuf;
  266.  
  267.    /* This is the same compression loop as in png_write_row() */
  268.    do
  269.    {
  270.       /* Compress the data */
  271.       ret = deflate(&png_ptr->zstream, Z_NO_FLUSH);
  272.  
  273.       if (ret != Z_OK)
  274.       {
  275.          /* Error */
  276.          if (png_ptr->zstream.msg != NULL)
  277.             png_error(png_ptr, png_ptr->zstream.msg);
  278.  
  279.          else
  280.             png_error(png_ptr, "zlib error");
  281.       }
  282.  
  283.       /* Check to see if we need more room */
  284.       if (!(png_ptr->zstream.avail_out))
  285.       {
  286.          /* Make sure the output array has room */
  287.          if (comp->num_output_ptr >= comp->max_output_ptr)
  288.          {
  289.             int old_max;
  290.  
  291.             old_max = comp->max_output_ptr;
  292.             comp->max_output_ptr = comp->num_output_ptr + 4;
  293.             if (comp->output_ptr != NULL)
  294.             {
  295.                png_bytepp old_ptr;
  296.  
  297.                old_ptr = comp->output_ptr;
  298.  
  299.                comp->output_ptr = (png_bytepp)png_malloc(png_ptr,
  300.                    (png_alloc_size_t)
  301.                    (comp->max_output_ptr * png_sizeof(png_charpp)));
  302.  
  303.                png_memcpy(comp->output_ptr, old_ptr, old_max
  304.                    * png_sizeof(png_charp));
  305.  
  306.                png_free(png_ptr, old_ptr);
  307.             }
  308.             else
  309.                comp->output_ptr = (png_bytepp)png_malloc(png_ptr,
  310.                    (png_alloc_size_t)
  311.                    (comp->max_output_ptr * png_sizeof(png_charp)));
  312.          }
  313.  
  314.          /* Save the data */
  315.          comp->output_ptr[comp->num_output_ptr] =
  316.              (png_bytep)png_malloc(png_ptr,
  317.              (png_alloc_size_t)png_ptr->zbuf_size);
  318.  
  319.          png_memcpy(comp->output_ptr[comp->num_output_ptr], png_ptr->zbuf,
  320.              png_ptr->zbuf_size);
  321.  
  322.          comp->num_output_ptr++;
  323.  
  324.          /* and reset the buffer */
  325.          png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
  326.          png_ptr->zstream.next_out = png_ptr->zbuf;
  327.       }
  328.    /* Continue until we don't have any more to compress */
  329.    } while (png_ptr->zstream.avail_in);
  330.  
  331.    /* Finish the compression */
  332.    do
  333.    {
  334.       /* Tell zlib we are finished */
  335.       ret = deflate(&png_ptr->zstream, Z_FINISH);
  336.  
  337.       if (ret == Z_OK)
  338.       {
  339.          /* Check to see if we need more room */
  340.          if (!(png_ptr->zstream.avail_out))
  341.          {
  342.             /* Check to make sure our output array has room */
  343.             if (comp->num_output_ptr >= comp->max_output_ptr)
  344.             {
  345.                int old_max;
  346.  
  347.                old_max = comp->max_output_ptr;
  348.                comp->max_output_ptr = comp->num_output_ptr + 4;
  349.                if (comp->output_ptr != NULL)
  350.                {
  351.                   png_bytepp old_ptr;
  352.  
  353.                   old_ptr = comp->output_ptr;
  354.  
  355.                   /* This could be optimized to realloc() */
  356.                   comp->output_ptr = (png_bytepp)png_malloc(png_ptr,
  357.                       (png_alloc_size_t)(comp->max_output_ptr *
  358.                       png_sizeof(png_charp)));
  359.  
  360.                   png_memcpy(comp->output_ptr, old_ptr,
  361.                       old_max * png_sizeof(png_charp));
  362.  
  363.                   png_free(png_ptr, old_ptr);
  364.                }
  365.  
  366.                else
  367.                   comp->output_ptr = (png_bytepp)png_malloc(png_ptr,
  368.                       (png_alloc_size_t)(comp->max_output_ptr *
  369.                       png_sizeof(png_charp)));
  370.             }
  371.  
  372.             /* Save the data */
  373.             comp->output_ptr[comp->num_output_ptr] =
  374.                 (png_bytep)png_malloc(png_ptr,
  375.                 (png_alloc_size_t)png_ptr->zbuf_size);
  376.  
  377.             png_memcpy(comp->output_ptr[comp->num_output_ptr], png_ptr->zbuf,
  378.                 png_ptr->zbuf_size);
  379.  
  380.             comp->num_output_ptr++;
  381.  
  382.             /* and reset the buffer pointers */
  383.             png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
  384.             png_ptr->zstream.next_out = png_ptr->zbuf;
  385.          }
  386.       }
  387.       else if (ret != Z_STREAM_END)
  388.       {
  389.          /* We got an error */
  390.          if (png_ptr->zstream.msg != NULL)
  391.             png_error(png_ptr, png_ptr->zstream.msg);
  392.  
  393.          else
  394.             png_error(png_ptr, "zlib error");
  395.       }
  396.    } while (ret != Z_STREAM_END);
  397.  
  398.    /* Text length is number of buffers plus last buffer */
  399.    text_len = png_ptr->zbuf_size * comp->num_output_ptr;
  400.  
  401.    if (png_ptr->zstream.avail_out < png_ptr->zbuf_size)
  402.       text_len += png_ptr->zbuf_size - (png_size_t)png_ptr->zstream.avail_out;
  403.  
  404.    return((int)text_len);
  405. }
  406.  
  407. /* Ship the compressed text out via chunk writes */
  408. static void /* PRIVATE */
  409. png_write_compressed_data_out(png_structp png_ptr, compression_state *comp)
  410. {
  411.    int i;
  412.  
  413.    /* Handle the no-compression case */
  414.    if (comp->input)
  415.    {
  416.       png_write_chunk_data(png_ptr, comp->input, comp->input_len);
  417.  
  418.       return;
  419.    }
  420.  
  421.    /* Write saved output buffers, if any */
  422.    for (i = 0; i < comp->num_output_ptr; i++)
  423.    {
  424.       png_write_chunk_data(png_ptr, comp->output_ptr[i],
  425.           (png_size_t)png_ptr->zbuf_size);
  426.  
  427.       png_free(png_ptr, comp->output_ptr[i]);
  428.    }
  429.  
  430.    if (comp->max_output_ptr != 0)
  431.       png_free(png_ptr, comp->output_ptr);
  432.  
  433.    /* Write anything left in zbuf */
  434.    if (png_ptr->zstream.avail_out < (png_uint_32)png_ptr->zbuf_size)
  435.       png_write_chunk_data(png_ptr, png_ptr->zbuf,
  436.           (png_size_t)(png_ptr->zbuf_size - png_ptr->zstream.avail_out));
  437.  
  438.    /* Reset zlib for another zTXt/iTXt or image data */
  439.    deflateReset(&png_ptr->zstream);
  440.    png_ptr->zstream.data_type = Z_BINARY;
  441. }
  442. #endif
  443.  
  444. /* Write the IHDR chunk, and update the png_struct with the necessary
  445.  * information.  Note that the rest of this code depends upon this
  446.  * information being correct.
  447.  */
  448. void /* PRIVATE */
  449. png_write_IHDR(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
  450.     int bit_depth, int color_type, int compression_type, int filter_type,
  451.     int interlace_type)
  452. {
  453.    PNG_IHDR;
  454.    int ret;
  455.  
  456.    png_byte buf[13]; /* Buffer to store the IHDR info */
  457.  
  458.    png_debug(1, "in png_write_IHDR");
  459.  
  460.    /* Check that we have valid input data from the application info */
  461.    switch (color_type)
  462.    {
  463.       case PNG_COLOR_TYPE_GRAY:
  464.          switch (bit_depth)
  465.          {
  466.             case 1:
  467.             case 2:
  468.             case 4:
  469.             case 8:
  470. #ifdef PNG_WRITE_16BIT_SUPPORTED
  471.             case 16:
  472. #endif
  473.                png_ptr->channels = 1; break;
  474.  
  475.             default:
  476.                png_error(png_ptr,
  477.                    "Invalid bit depth for grayscale image");
  478.          }
  479.          break;
  480.  
  481.       case PNG_COLOR_TYPE_RGB:
  482. #ifdef PNG_WRITE_16BIT_SUPPORTED
  483.          if (bit_depth != 8 && bit_depth != 16)
  484. #else
  485.          if (bit_depth != 8)
  486. #endif
  487.             png_error(png_ptr, "Invalid bit depth for RGB image");
  488.  
  489.          png_ptr->channels = 3;
  490.          break;
  491.  
  492.       case PNG_COLOR_TYPE_PALETTE:
  493.          switch (bit_depth)
  494.          {
  495.             case 1:
  496.             case 2:
  497.             case 4:
  498.             case 8:
  499.                png_ptr->channels = 1;
  500.                break;
  501.  
  502.             default:
  503.                png_error(png_ptr, "Invalid bit depth for paletted image");
  504.          }
  505.          break;
  506.  
  507.       case PNG_COLOR_TYPE_GRAY_ALPHA:
  508.          if (bit_depth != 8 && bit_depth != 16)
  509.             png_error(png_ptr, "Invalid bit depth for grayscale+alpha image");
  510.  
  511.          png_ptr->channels = 2;
  512.          break;
  513.  
  514.       case PNG_COLOR_TYPE_RGB_ALPHA:
  515. #ifdef PNG_WRITE_16BIT_SUPPORTED
  516.          if (bit_depth != 8 && bit_depth != 16)
  517. #else
  518.          if (bit_depth != 8)
  519. #endif
  520.             png_error(png_ptr, "Invalid bit depth for RGBA image");
  521.  
  522.          png_ptr->channels = 4;
  523.          break;
  524.  
  525.       default:
  526.          png_error(png_ptr, "Invalid image color type specified");
  527.    }
  528.  
  529.    if (compression_type != PNG_COMPRESSION_TYPE_BASE)
  530.    {
  531.       png_warning(png_ptr, "Invalid compression type specified");
  532.       compression_type = PNG_COMPRESSION_TYPE_BASE;
  533.    }
  534.  
  535.    /* Write filter_method 64 (intrapixel differencing) only if
  536.     * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
  537.     * 2. Libpng did not write a PNG signature (this filter_method is only
  538.     *    used in PNG datastreams that are embedded in MNG datastreams) and
  539.     * 3. The application called png_permit_mng_features with a mask that
  540.     *    included PNG_FLAG_MNG_FILTER_64 and
  541.     * 4. The filter_method is 64 and
  542.     * 5. The color_type is RGB or RGBA
  543.     */
  544.    if (
  545. #ifdef PNG_MNG_FEATURES_SUPPORTED
  546.        !((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
  547.        ((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE) == 0) &&
  548.        (color_type == PNG_COLOR_TYPE_RGB ||
  549.         color_type == PNG_COLOR_TYPE_RGB_ALPHA) &&
  550.        (filter_type == PNG_INTRAPIXEL_DIFFERENCING)) &&
  551. #endif
  552.        filter_type != PNG_FILTER_TYPE_BASE)
  553.    {
  554.       png_warning(png_ptr, "Invalid filter type specified");
  555.       filter_type = PNG_FILTER_TYPE_BASE;
  556.    }
  557.  
  558. #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  559.    if (interlace_type != PNG_INTERLACE_NONE &&
  560.        interlace_type != PNG_INTERLACE_ADAM7)
  561.    {
  562.       png_warning(png_ptr, "Invalid interlace type specified");
  563.       interlace_type = PNG_INTERLACE_ADAM7;
  564.    }
  565. #else
  566.    interlace_type=PNG_INTERLACE_NONE;
  567. #endif
  568.  
  569.    /* Save the relevent information */
  570.    png_ptr->bit_depth = (png_byte)bit_depth;
  571.    png_ptr->color_type = (png_byte)color_type;
  572.    png_ptr->interlaced = (png_byte)interlace_type;
  573. #ifdef PNG_MNG_FEATURES_SUPPORTED
  574.    png_ptr->filter_type = (png_byte)filter_type;
  575. #endif
  576.    png_ptr->compression_type = (png_byte)compression_type;
  577.    png_ptr->width = width;
  578.    png_ptr->height = height;
  579.  
  580.    png_ptr->pixel_depth = (png_byte)(bit_depth * png_ptr->channels);
  581.    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
  582.    /* Set the usr info, so any transformations can modify it */
  583.    png_ptr->usr_width = png_ptr->width;
  584.    png_ptr->usr_bit_depth = png_ptr->bit_depth;
  585.    png_ptr->usr_channels = png_ptr->channels;
  586.  
  587.    /* Pack the header information into the buffer */
  588.    png_save_uint_32(buf, width);
  589.    png_save_uint_32(buf + 4, height);
  590.    buf[8] = (png_byte)bit_depth;
  591.    buf[9] = (png_byte)color_type;
  592.    buf[10] = (png_byte)compression_type;
  593.    buf[11] = (png_byte)filter_type;
  594.    buf[12] = (png_byte)interlace_type;
  595.  
  596.    /* Write the chunk */
  597.    png_write_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
  598.  
  599.    /* Initialize zlib with PNG info */
  600.    png_ptr->zstream.zalloc = png_zalloc;
  601.    png_ptr->zstream.zfree = png_zfree;
  602.    png_ptr->zstream.opaque = (voidpf)png_ptr;
  603.  
  604.    if (!(png_ptr->do_filter))
  605.    {
  606.       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
  607.           png_ptr->bit_depth < 8)
  608.          png_ptr->do_filter = PNG_FILTER_NONE;
  609.  
  610.       else
  611.          png_ptr->do_filter = PNG_ALL_FILTERS;
  612.    }
  613.  
  614.    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_STRATEGY))
  615.    {
  616.       if (png_ptr->do_filter != PNG_FILTER_NONE)
  617.          png_ptr->zlib_strategy = Z_FILTERED;
  618.  
  619.       else
  620.          png_ptr->zlib_strategy = Z_DEFAULT_STRATEGY;
  621.    }
  622.  
  623.    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_LEVEL))
  624.       png_ptr->zlib_level = Z_DEFAULT_COMPRESSION;
  625.  
  626.    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_MEM_LEVEL))
  627.       png_ptr->zlib_mem_level = 8;
  628.  
  629.    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_WINDOW_BITS))
  630.       png_ptr->zlib_window_bits = 15;
  631.  
  632.    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_METHOD))
  633.       png_ptr->zlib_method = 8;
  634.  
  635.    ret = deflateInit2(&png_ptr->zstream, png_ptr->zlib_level,
  636.        png_ptr->zlib_method, png_ptr->zlib_window_bits,
  637.        png_ptr->zlib_mem_level, png_ptr->zlib_strategy);
  638.  
  639.    if (ret != Z_OK)
  640.    {
  641.       if (ret == Z_VERSION_ERROR)
  642.          png_error(png_ptr,
  643.             "zlib failed to initialize compressor -- version error");
  644.  
  645.       if (ret == Z_STREAM_ERROR)
  646.          png_error(png_ptr,
  647.              "zlib failed to initialize compressor -- stream error");
  648.  
  649.       if (ret == Z_MEM_ERROR)
  650.          png_error(png_ptr,
  651.              "zlib failed to initialize compressor -- mem error");
  652.  
  653.       png_error(png_ptr, "zlib failed to initialize compressor");
  654.    }
  655.  
  656.    png_ptr->zstream.next_out = png_ptr->zbuf;
  657.    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
  658.    /* libpng is not interested in zstream.data_type, so set it
  659.     * to a predefined value, to avoid its evaluation inside zlib
  660.     */
  661.    png_ptr->zstream.data_type = Z_BINARY;
  662.  
  663.    png_ptr->mode = PNG_HAVE_IHDR;
  664. }
  665.  
  666. /* Write the palette.  We are careful not to trust png_color to be in the
  667.  * correct order for PNG, so people can redefine it to any convenient
  668.  * structure.
  669.  */
  670. void /* PRIVATE */
  671. png_write_PLTE(png_structp png_ptr, png_const_colorp palette,
  672.     png_uint_32 num_pal)
  673. {
  674.    PNG_PLTE;
  675.    png_uint_32 i;
  676.    png_const_colorp pal_ptr;
  677.    png_byte buf[3];
  678.  
  679.    png_debug(1, "in png_write_PLTE");
  680.  
  681.    if ((
  682. #ifdef PNG_MNG_FEATURES_SUPPORTED
  683.        !(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) &&
  684. #endif
  685.        num_pal == 0) || num_pal > 256)
  686.    {
  687.       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
  688.       {
  689.          png_error(png_ptr, "Invalid number of colors in palette");
  690.       }
  691.  
  692.       else
  693.       {
  694.          png_warning(png_ptr, "Invalid number of colors in palette");
  695.          return;
  696.       }
  697.    }
  698.  
  699.    if (!(png_ptr->color_type&PNG_COLOR_MASK_COLOR))
  700.    {
  701.       png_warning(png_ptr,
  702.           "Ignoring request to write a PLTE chunk in grayscale PNG");
  703.  
  704.       return;
  705.    }
  706.  
  707.    png_ptr->num_palette = (png_uint_16)num_pal;
  708.    png_debug1(3, "num_palette = %d", png_ptr->num_palette);
  709.  
  710.    png_write_chunk_start(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
  711. #ifdef PNG_POINTER_INDEXING_SUPPORTED
  712.  
  713.    for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
  714.    {
  715.       buf[0] = pal_ptr->red;
  716.       buf[1] = pal_ptr->green;
  717.       buf[2] = pal_ptr->blue;
  718.       png_write_chunk_data(png_ptr, buf, (png_size_t)3);
  719.    }
  720.  
  721. #else
  722.    /* This is a little slower but some buggy compilers need to do this
  723.     * instead
  724.     */
  725.    pal_ptr=palette;
  726.  
  727.    for (i = 0; i < num_pal; i++)
  728.    {
  729.       buf[0] = pal_ptr[i].red;
  730.       buf[1] = pal_ptr[i].green;
  731.       buf[2] = pal_ptr[i].blue;
  732.       png_write_chunk_data(png_ptr, buf, (png_size_t)3);
  733.    }
  734.  
  735. #endif
  736.    png_write_chunk_end(png_ptr);
  737.    png_ptr->mode |= PNG_HAVE_PLTE;
  738. }
  739.  
  740. /* Write an IDAT chunk */
  741. void /* PRIVATE */
  742. png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
  743. {
  744.    PNG_IDAT;
  745.  
  746.    png_debug(1, "in png_write_IDAT");
  747.  
  748.    /* Optimize the CMF field in the zlib stream. */
  749.    /* This hack of the zlib stream is compliant to the stream specification. */
  750.    if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
  751.        png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
  752.    {
  753.       unsigned int z_cmf = data[0];  /* zlib compression method and flags */
  754.       if ((z_cmf & 0x0f) == 8 && (z_cmf & 0xf0) <= 0x70)
  755.       {
  756.          /* Avoid memory underflows and multiplication overflows.
  757.           *
  758.           * The conditions below are practically always satisfied;
  759.           * however, they still must be checked.
  760.           */
  761.          if (length >= 2 &&
  762.              png_ptr->height < 16384 && png_ptr->width < 16384)
  763.          {
  764.             png_uint_32 uncompressed_idat_size = png_ptr->height *
  765.                 ((png_ptr->width *
  766.                 png_ptr->channels * png_ptr->bit_depth + 15) >> 3);
  767.             unsigned int z_cinfo = z_cmf >> 4;
  768.             unsigned int half_z_window_size = 1 << (z_cinfo + 7);
  769.             while (uncompressed_idat_size <= half_z_window_size &&
  770.                 half_z_window_size >= 256)
  771.             {
  772.                z_cinfo--;
  773.                half_z_window_size >>= 1;
  774.             }
  775.  
  776.             z_cmf = (z_cmf & 0x0f) | (z_cinfo << 4);
  777.  
  778.             if (data[0] != z_cmf)
  779.             {
  780.                int tmp;
  781.                data[0] = (png_byte)z_cmf;
  782.                tmp = data[1] & 0xe0;
  783.                tmp += 0x1f - ((z_cmf << 8) + tmp) % 0x1f;
  784.                data[1] = (png_byte)tmp;
  785.             }
  786.          }
  787.       }
  788.  
  789.       else
  790.          png_error(png_ptr,
  791.              "Invalid zlib compression method or flags in IDAT");
  792.    }
  793.  
  794.    png_write_chunk(png_ptr, png_IDAT, data, length);
  795.    png_ptr->mode |= PNG_HAVE_IDAT;
  796. }
  797.  
  798. /* Write an IEND chunk */
  799. void /* PRIVATE */
  800. png_write_IEND(png_structp png_ptr)
  801. {
  802.    PNG_IEND;
  803.  
  804.    png_debug(1, "in png_write_IEND");
  805.  
  806.    png_write_chunk(png_ptr, png_IEND, NULL, (png_size_t)0);
  807.    png_ptr->mode |= PNG_HAVE_IEND;
  808. }
  809.  
  810. #ifdef PNG_WRITE_gAMA_SUPPORTED
  811. /* Write a gAMA chunk */
  812. void /* PRIVATE */
  813. png_write_gAMA_fixed(png_structp png_ptr, png_fixed_point file_gamma)
  814. {
  815.    PNG_gAMA;
  816.    png_byte buf[4];
  817.  
  818.    png_debug(1, "in png_write_gAMA");
  819.  
  820.    /* file_gamma is saved in 1/100,000ths */
  821.    png_save_uint_32(buf, (png_uint_32)file_gamma);
  822.    png_write_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
  823. }
  824. #endif
  825.  
  826. #ifdef PNG_WRITE_sRGB_SUPPORTED
  827. /* Write a sRGB chunk */
  828. void /* PRIVATE */
  829. png_write_sRGB(png_structp png_ptr, int srgb_intent)
  830. {
  831.    PNG_sRGB;
  832.    png_byte buf[1];
  833.  
  834.    png_debug(1, "in png_write_sRGB");
  835.  
  836.    if (srgb_intent >= PNG_sRGB_INTENT_LAST)
  837.       png_warning(png_ptr,
  838.           "Invalid sRGB rendering intent specified");
  839.  
  840.    buf[0]=(png_byte)srgb_intent;
  841.    png_write_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
  842. }
  843. #endif
  844.  
  845. #ifdef PNG_WRITE_iCCP_SUPPORTED
  846. /* Write an iCCP chunk */
  847. void /* PRIVATE */
  848. png_write_iCCP(png_structp png_ptr, png_const_charp name, int compression_type,
  849.     png_const_charp profile, int profile_len)
  850. {
  851.    PNG_iCCP;
  852.    png_size_t name_len;
  853.    png_charp new_name;
  854.    compression_state comp;
  855.    int embedded_profile_len = 0;
  856.  
  857.    png_debug(1, "in png_write_iCCP");
  858.  
  859.    comp.num_output_ptr = 0;
  860.    comp.max_output_ptr = 0;
  861.    comp.output_ptr = NULL;
  862.    comp.input = NULL;
  863.    comp.input_len = 0;
  864.  
  865.    if ((name_len = png_check_keyword(png_ptr, name, &new_name)) == 0)
  866.       return;
  867.  
  868.    if (compression_type != PNG_COMPRESSION_TYPE_BASE)
  869.       png_warning(png_ptr, "Unknown compression type in iCCP chunk");
  870.  
  871.    if (profile == NULL)
  872.       profile_len = 0;
  873.  
  874.    if (profile_len > 3)
  875.       embedded_profile_len =
  876.           ((*( (png_const_bytep)profile    ))<<24) |
  877.           ((*( (png_const_bytep)profile + 1))<<16) |
  878.           ((*( (png_const_bytep)profile + 2))<< 8) |
  879.           ((*( (png_const_bytep)profile + 3))    );
  880.  
  881.    if (embedded_profile_len < 0)
  882.    {
  883.       png_warning(png_ptr,
  884.           "Embedded profile length in iCCP chunk is negative");
  885.  
  886.       png_free(png_ptr, new_name);
  887.       return;
  888.    }
  889.  
  890.    if (profile_len < embedded_profile_len)
  891.    {
  892.       png_warning(png_ptr,
  893.           "Embedded profile length too large in iCCP chunk");
  894.  
  895.       png_free(png_ptr, new_name);
  896.       return;
  897.    }
  898.  
  899.    if (profile_len > embedded_profile_len)
  900.    {
  901.       png_warning(png_ptr,
  902.           "Truncating profile to actual length in iCCP chunk");
  903.  
  904.       profile_len = embedded_profile_len;
  905.    }
  906.  
  907.    if (profile_len)
  908.       profile_len = png_text_compress(png_ptr, profile,
  909.           (png_size_t)profile_len, PNG_COMPRESSION_TYPE_BASE, &comp);
  910.  
  911.    /* Make sure we include the NULL after the name and the compression type */
  912.    png_write_chunk_start(png_ptr, png_iCCP,
  913.        (png_uint_32)(name_len + profile_len + 2));
  914.  
  915.    new_name[name_len + 1] = 0x00;
  916.  
  917.    png_write_chunk_data(png_ptr, (png_bytep)new_name,
  918.        (png_size_t)(name_len + 2));
  919.  
  920.    if (profile_len)
  921.       png_write_compressed_data_out(png_ptr, &comp);
  922.  
  923.    png_write_chunk_end(png_ptr);
  924.    png_free(png_ptr, new_name);
  925. }
  926. #endif
  927.  
  928. #ifdef PNG_WRITE_sPLT_SUPPORTED
  929. /* Write a sPLT chunk */
  930. void /* PRIVATE */
  931. png_write_sPLT(png_structp png_ptr, png_const_sPLT_tp spalette)
  932. {
  933.    PNG_sPLT;
  934.    png_size_t name_len;
  935.    png_charp new_name;
  936.    png_byte entrybuf[10];
  937.    png_size_t entry_size = (spalette->depth == 8 ? 6 : 10);
  938.    png_size_t palette_size = entry_size * spalette->nentries;
  939.    png_sPLT_entryp ep;
  940. #ifndef PNG_POINTER_INDEXING_SUPPORTED
  941.    int i;
  942. #endif
  943.  
  944.    png_debug(1, "in png_write_sPLT");
  945.  
  946.    if ((name_len = png_check_keyword(png_ptr,spalette->name, &new_name))==0)
  947.       return;
  948.  
  949.    /* Make sure we include the NULL after the name */
  950.    png_write_chunk_start(png_ptr, png_sPLT,
  951.        (png_uint_32)(name_len + 2 + palette_size));
  952.  
  953.    png_write_chunk_data(png_ptr, (png_bytep)new_name,
  954.        (png_size_t)(name_len + 1));
  955.  
  956.    png_write_chunk_data(png_ptr, &spalette->depth, (png_size_t)1);
  957.  
  958.    /* Loop through each palette entry, writing appropriately */
  959. #ifdef PNG_POINTER_INDEXING_SUPPORTED
  960.    for (ep = spalette->entries; ep<spalette->entries + spalette->nentries; ep++)
  961.    {
  962.       if (spalette->depth == 8)
  963.       {
  964.          entrybuf[0] = (png_byte)ep->red;
  965.          entrybuf[1] = (png_byte)ep->green;
  966.          entrybuf[2] = (png_byte)ep->blue;
  967.          entrybuf[3] = (png_byte)ep->alpha;
  968.          png_save_uint_16(entrybuf + 4, ep->frequency);
  969.       }
  970.  
  971.       else
  972.       {
  973.          png_save_uint_16(entrybuf + 0, ep->red);
  974.          png_save_uint_16(entrybuf + 2, ep->green);
  975.          png_save_uint_16(entrybuf + 4, ep->blue);
  976.          png_save_uint_16(entrybuf + 6, ep->alpha);
  977.          png_save_uint_16(entrybuf + 8, ep->frequency);
  978.       }
  979.  
  980.       png_write_chunk_data(png_ptr, entrybuf, (png_size_t)entry_size);
  981.    }
  982. #else
  983.    ep=spalette->entries;
  984.    for (i = 0; i>spalette->nentries; i++)
  985.    {
  986.       if (spalette->depth == 8)
  987.       {
  988.          entrybuf[0] = (png_byte)ep[i].red;
  989.          entrybuf[1] = (png_byte)ep[i].green;
  990.          entrybuf[2] = (png_byte)ep[i].blue;
  991.          entrybuf[3] = (png_byte)ep[i].alpha;
  992.          png_save_uint_16(entrybuf + 4, ep[i].frequency);
  993.       }
  994.  
  995.       else
  996.       {
  997.          png_save_uint_16(entrybuf + 0, ep[i].red);
  998.          png_save_uint_16(entrybuf + 2, ep[i].green);
  999.          png_save_uint_16(entrybuf + 4, ep[i].blue);
  1000.          png_save_uint_16(entrybuf + 6, ep[i].alpha);
  1001.          png_save_uint_16(entrybuf + 8, ep[i].frequency);
  1002.       }
  1003.  
  1004.       png_write_chunk_data(png_ptr, entrybuf, (png_size_t)entry_size);
  1005.    }
  1006. #endif
  1007.  
  1008.    png_write_chunk_end(png_ptr);
  1009.    png_free(png_ptr, new_name);
  1010. }
  1011. #endif
  1012.  
  1013. #ifdef PNG_WRITE_sBIT_SUPPORTED
  1014. /* Write the sBIT chunk */
  1015. void /* PRIVATE */
  1016. png_write_sBIT(png_structp png_ptr, png_const_color_8p sbit, int color_type)
  1017. {
  1018.    PNG_sBIT;
  1019.    png_byte buf[4];
  1020.    png_size_t size;
  1021.  
  1022.    png_debug(1, "in png_write_sBIT");
  1023.  
  1024.    /* Make sure we don't depend upon the order of PNG_COLOR_8 */
  1025.    if (color_type & PNG_COLOR_MASK_COLOR)
  1026.    {
  1027.       png_byte maxbits;
  1028.  
  1029.       maxbits = (png_byte)(color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
  1030.           png_ptr->usr_bit_depth);
  1031.  
  1032.       if (sbit->red == 0 || sbit->red > maxbits ||
  1033.           sbit->green == 0 || sbit->green > maxbits ||
  1034.           sbit->blue == 0 || sbit->blue > maxbits)
  1035.       {
  1036.          png_warning(png_ptr, "Invalid sBIT depth specified");
  1037.          return;
  1038.       }
  1039.  
  1040.       buf[0] = sbit->red;
  1041.       buf[1] = sbit->green;
  1042.       buf[2] = sbit->blue;
  1043.       size = 3;
  1044.    }
  1045.  
  1046.    else
  1047.    {
  1048.       if (sbit->gray == 0 || sbit->gray > png_ptr->usr_bit_depth)
  1049.       {
  1050.          png_warning(png_ptr, "Invalid sBIT depth specified");
  1051.          return;
  1052.       }
  1053.  
  1054.       buf[0] = sbit->gray;
  1055.       size = 1;
  1056.    }
  1057.  
  1058.    if (color_type & PNG_COLOR_MASK_ALPHA)
  1059.    {
  1060.       if (sbit->alpha == 0 || sbit->alpha > png_ptr->usr_bit_depth)
  1061.       {
  1062.          png_warning(png_ptr, "Invalid sBIT depth specified");
  1063.          return;
  1064.       }
  1065.  
  1066.       buf[size++] = sbit->alpha;
  1067.    }
  1068.  
  1069.    png_write_chunk(png_ptr, png_sBIT, buf, size);
  1070. }
  1071. #endif
  1072.  
  1073. #ifdef PNG_WRITE_cHRM_SUPPORTED
  1074. /* Write the cHRM chunk */
  1075. void /* PRIVATE */
  1076. png_write_cHRM_fixed(png_structp png_ptr, png_fixed_point white_x,
  1077.     png_fixed_point white_y, png_fixed_point red_x, png_fixed_point red_y,
  1078.     png_fixed_point green_x, png_fixed_point green_y, png_fixed_point blue_x,
  1079.     png_fixed_point blue_y)
  1080. {
  1081.    PNG_cHRM;
  1082.    png_byte buf[32];
  1083.  
  1084.    png_debug(1, "in png_write_cHRM");
  1085.  
  1086.    /* Each value is saved in 1/100,000ths */
  1087. #ifdef PNG_CHECK_cHRM_SUPPORTED
  1088.    if (png_check_cHRM_fixed(png_ptr, white_x, white_y, red_x, red_y,
  1089.        green_x, green_y, blue_x, blue_y))
  1090. #endif
  1091.    {
  1092.       png_save_uint_32(buf, (png_uint_32)white_x);
  1093.       png_save_uint_32(buf + 4, (png_uint_32)white_y);
  1094.  
  1095.       png_save_uint_32(buf + 8, (png_uint_32)red_x);
  1096.       png_save_uint_32(buf + 12, (png_uint_32)red_y);
  1097.  
  1098.       png_save_uint_32(buf + 16, (png_uint_32)green_x);
  1099.       png_save_uint_32(buf + 20, (png_uint_32)green_y);
  1100.  
  1101.       png_save_uint_32(buf + 24, (png_uint_32)blue_x);
  1102.       png_save_uint_32(buf + 28, (png_uint_32)blue_y);
  1103.  
  1104.       png_write_chunk(png_ptr, png_cHRM, buf, (png_size_t)32);
  1105.    }
  1106. }
  1107. #endif
  1108.  
  1109. #ifdef PNG_WRITE_tRNS_SUPPORTED
  1110. /* Write the tRNS chunk */
  1111. void /* PRIVATE */
  1112. png_write_tRNS(png_structp png_ptr, png_const_bytep trans_alpha,
  1113.     png_const_color_16p tran, int num_trans, int color_type)
  1114. {
  1115.    PNG_tRNS;
  1116.    png_byte buf[6];
  1117.  
  1118.    png_debug(1, "in png_write_tRNS");
  1119.  
  1120.    if (color_type == PNG_COLOR_TYPE_PALETTE)
  1121.    {
  1122.       if (num_trans <= 0 || num_trans > (int)png_ptr->num_palette)
  1123.       {
  1124.          png_warning(png_ptr, "Invalid number of transparent colors specified");
  1125.          return;
  1126.       }
  1127.  
  1128.       /* Write the chunk out as it is */
  1129.       png_write_chunk(png_ptr, png_tRNS, trans_alpha, (png_size_t)num_trans);
  1130.    }
  1131.  
  1132.    else if (color_type == PNG_COLOR_TYPE_GRAY)
  1133.    {
  1134.       /* One 16 bit value */
  1135.       if (tran->gray >= (1 << png_ptr->bit_depth))
  1136.       {
  1137.          png_warning(png_ptr,
  1138.              "Ignoring attempt to write tRNS chunk out-of-range for bit_depth");
  1139.  
  1140.          return;
  1141.       }
  1142.  
  1143.       png_save_uint_16(buf, tran->gray);
  1144.       png_write_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
  1145.    }
  1146.  
  1147.    else if (color_type == PNG_COLOR_TYPE_RGB)
  1148.    {
  1149.       /* Three 16 bit values */
  1150.       png_save_uint_16(buf, tran->red);
  1151.       png_save_uint_16(buf + 2, tran->green);
  1152.       png_save_uint_16(buf + 4, tran->blue);
  1153. #ifdef PNG_WRITE_16BIT_SUPPORTED
  1154.       if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
  1155. #else
  1156.       if (buf[0] | buf[2] | buf[4])
  1157. #endif
  1158.       {
  1159.          png_warning(png_ptr,
  1160.            "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
  1161.          return;
  1162.       }
  1163.  
  1164.       png_write_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
  1165.    }
  1166.  
  1167.    else
  1168.    {
  1169.       png_warning(png_ptr, "Can't write tRNS with an alpha channel");
  1170.    }
  1171. }
  1172. #endif
  1173.  
  1174. #ifdef PNG_WRITE_bKGD_SUPPORTED
  1175. /* Write the background chunk */
  1176. void /* PRIVATE */
  1177. png_write_bKGD(png_structp png_ptr, png_const_color_16p back, int color_type)
  1178. {
  1179.    PNG_bKGD;
  1180.    png_byte buf[6];
  1181.  
  1182.    png_debug(1, "in png_write_bKGD");
  1183.  
  1184.    if (color_type == PNG_COLOR_TYPE_PALETTE)
  1185.    {
  1186.       if (
  1187. #ifdef PNG_MNG_FEATURES_SUPPORTED
  1188.           (png_ptr->num_palette ||
  1189.           (!(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE))) &&
  1190. #endif
  1191.          back->index >= png_ptr->num_palette)
  1192.       {
  1193.          png_warning(png_ptr, "Invalid background palette index");
  1194.          return;
  1195.       }
  1196.  
  1197.       buf[0] = back->index;
  1198.       png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
  1199.    }
  1200.  
  1201.    else if (color_type & PNG_COLOR_MASK_COLOR)
  1202.    {
  1203.       png_save_uint_16(buf, back->red);
  1204.       png_save_uint_16(buf + 2, back->green);
  1205.       png_save_uint_16(buf + 4, back->blue);
  1206. #ifdef PNG_WRITE_16BIT_SUPPORTED
  1207.       if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
  1208. #else
  1209.       if (buf[0] | buf[2] | buf[4])
  1210. #endif
  1211.       {
  1212.          png_warning(png_ptr,
  1213.              "Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
  1214.  
  1215.          return;
  1216.       }
  1217.  
  1218.       png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
  1219.    }
  1220.  
  1221.    else
  1222.    {
  1223.       if (back->gray >= (1 << png_ptr->bit_depth))
  1224.       {
  1225.          png_warning(png_ptr,
  1226.              "Ignoring attempt to write bKGD chunk out-of-range for bit_depth");
  1227.  
  1228.          return;
  1229.       }
  1230.  
  1231.       png_save_uint_16(buf, back->gray);
  1232.       png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
  1233.    }
  1234. }
  1235. #endif
  1236.  
  1237. #ifdef PNG_WRITE_hIST_SUPPORTED
  1238. /* Write the histogram */
  1239. void /* PRIVATE */
  1240. png_write_hIST(png_structp png_ptr, png_const_uint_16p hist, int num_hist)
  1241. {
  1242.    PNG_hIST;
  1243.    int i;
  1244.    png_byte buf[3];
  1245.  
  1246.    png_debug(1, "in png_write_hIST");
  1247.  
  1248.    if (num_hist > (int)png_ptr->num_palette)
  1249.    {
  1250.       png_debug2(3, "num_hist = %d, num_palette = %d", num_hist,
  1251.           png_ptr->num_palette);
  1252.  
  1253.       png_warning(png_ptr, "Invalid number of histogram entries specified");
  1254.       return;
  1255.    }
  1256.  
  1257.    png_write_chunk_start(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
  1258.  
  1259.    for (i = 0; i < num_hist; i++)
  1260.    {
  1261.       png_save_uint_16(buf, hist[i]);
  1262.       png_write_chunk_data(png_ptr, buf, (png_size_t)2);
  1263.    }
  1264.  
  1265.    png_write_chunk_end(png_ptr);
  1266. }
  1267. #endif
  1268.  
  1269. #if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_pCAL_SUPPORTED) || \
  1270.     defined(PNG_WRITE_iCCP_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
  1271. /* Check that the tEXt or zTXt keyword is valid per PNG 1.0 specification,
  1272.  * and if invalid, correct the keyword rather than discarding the entire
  1273.  * chunk.  The PNG 1.0 specification requires keywords 1-79 characters in
  1274.  * length, forbids leading or trailing whitespace, multiple internal spaces,
  1275.  * and the non-break space (0x80) from ISO 8859-1.  Returns keyword length.
  1276.  *
  1277.  * The new_key is allocated to hold the corrected keyword and must be freed
  1278.  * by the calling routine.  This avoids problems with trying to write to
  1279.  * static keywords without having to have duplicate copies of the strings.
  1280.  */
  1281. png_size_t /* PRIVATE */
  1282. png_check_keyword(png_structp png_ptr, png_const_charp key, png_charpp new_key)
  1283. {
  1284.    png_size_t key_len;
  1285.    png_const_charp ikp;
  1286.    png_charp kp, dp;
  1287.    int kflag;
  1288.    int kwarn=0;
  1289.  
  1290.    png_debug(1, "in png_check_keyword");
  1291.  
  1292.    *new_key = NULL;
  1293.  
  1294.    if (key == NULL || (key_len = png_strlen(key)) == 0)
  1295.    {
  1296.       png_warning(png_ptr, "zero length keyword");
  1297.       return ((png_size_t)0);
  1298.    }
  1299.  
  1300.    png_debug1(2, "Keyword to be checked is '%s'", key);
  1301.  
  1302.    *new_key = (png_charp)png_malloc_warn(png_ptr, (png_uint_32)(key_len + 2));
  1303.  
  1304.    if (*new_key == NULL)
  1305.    {
  1306.       png_warning(png_ptr, "Out of memory while procesing keyword");
  1307.       return ((png_size_t)0);
  1308.    }
  1309.  
  1310.    /* Replace non-printing characters with a blank and print a warning */
  1311.    for (ikp = key, dp = *new_key; *ikp != '\0'; ikp++, dp++)
  1312.    {
  1313.       if ((png_byte)*ikp < 0x20 ||
  1314.          ((png_byte)*ikp > 0x7E && (png_byte)*ikp < 0xA1))
  1315.       {
  1316. #ifdef PNG_CONSOLE_IO_SUPPORTED
  1317.          char msg[40];
  1318.  
  1319.          png_snprintf(msg, 40,
  1320.              "invalid keyword character 0x%02X", (png_byte)*ikp);
  1321.          png_warning(png_ptr, msg);
  1322. #else
  1323.          png_warning(png_ptr, "invalid character in keyword");
  1324. #endif
  1325.          *dp = ' ';
  1326.       }
  1327.  
  1328.       else
  1329.       {
  1330.          *dp = *ikp;
  1331.       }
  1332.    }
  1333.    *dp = '\0';
  1334.  
  1335.    /* Remove any trailing white space. */
  1336.    kp = *new_key + key_len - 1;
  1337.    if (*kp == ' ')
  1338.    {
  1339.       png_warning(png_ptr, "trailing spaces removed from keyword");
  1340.  
  1341.       while (*kp == ' ')
  1342.       {
  1343.          *(kp--) = '\0';
  1344.          key_len--;
  1345.       }
  1346.    }
  1347.  
  1348.    /* Remove any leading white space. */
  1349.    kp = *new_key;
  1350.    if (*kp == ' ')
  1351.    {
  1352.       png_warning(png_ptr, "leading spaces removed from keyword");
  1353.  
  1354.       while (*kp == ' ')
  1355.       {
  1356.          kp++;
  1357.          key_len--;
  1358.       }
  1359.    }
  1360.  
  1361.    png_debug1(2, "Checking for multiple internal spaces in '%s'", kp);
  1362.  
  1363.    /* Remove multiple internal spaces. */
  1364.    for (kflag = 0, dp = *new_key; *kp != '\0'; kp++)
  1365.    {
  1366.       if (*kp == ' ' && kflag == 0)
  1367.       {
  1368.          *(dp++) = *kp;
  1369.          kflag = 1;
  1370.       }
  1371.  
  1372.       else if (*kp == ' ')
  1373.       {
  1374.          key_len--;
  1375.          kwarn = 1;
  1376.       }
  1377.  
  1378.       else
  1379.       {
  1380.          *(dp++) = *kp;
  1381.          kflag = 0;
  1382.       }
  1383.    }
  1384.    *dp = '\0';
  1385.    if (kwarn)
  1386.       png_warning(png_ptr, "extra interior spaces removed from keyword");
  1387.  
  1388.    if (key_len == 0)
  1389.    {
  1390.       png_free(png_ptr, *new_key);
  1391.       png_warning(png_ptr, "Zero length keyword");
  1392.    }
  1393.  
  1394.    if (key_len > 79)
  1395.    {
  1396.       png_warning(png_ptr, "keyword length must be 1 - 79 characters");
  1397.       (*new_key)[79] = '\0';
  1398.       key_len = 79;
  1399.    }
  1400.  
  1401.    return (key_len);
  1402. }
  1403. #endif
  1404.  
  1405. #ifdef PNG_WRITE_tEXt_SUPPORTED
  1406. /* Write a tEXt chunk */
  1407. void /* PRIVATE */
  1408. png_write_tEXt(png_structp png_ptr, png_const_charp key, png_const_charp text,
  1409.     png_size_t text_len)
  1410. {
  1411.    PNG_tEXt;
  1412.    png_size_t key_len;
  1413.    png_charp new_key;
  1414.  
  1415.    png_debug(1, "in png_write_tEXt");
  1416.  
  1417.    if ((key_len = png_check_keyword(png_ptr, key, &new_key))==0)
  1418.       return;
  1419.  
  1420.    if (text == NULL || *text == '\0')
  1421.       text_len = 0;
  1422.  
  1423.    else
  1424.       text_len = png_strlen(text);
  1425.  
  1426.    /* Make sure we include the 0 after the key */
  1427.    png_write_chunk_start(png_ptr, png_tEXt,
  1428.        (png_uint_32)(key_len + text_len + 1));
  1429.    /*
  1430.     * We leave it to the application to meet PNG-1.0 requirements on the
  1431.     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
  1432.     * any non-Latin-1 characters except for NEWLINE.  ISO PNG will forbid them.
  1433.     * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
  1434.     */
  1435.    png_write_chunk_data(png_ptr, (png_bytep)new_key,
  1436.        (png_size_t)(key_len + 1));
  1437.  
  1438.    if (text_len)
  1439.       png_write_chunk_data(png_ptr, (png_const_bytep)text,
  1440.           (png_size_t)text_len);
  1441.  
  1442.    png_write_chunk_end(png_ptr);
  1443.    png_free(png_ptr, new_key);
  1444. }
  1445. #endif
  1446.  
  1447. #ifdef PNG_WRITE_zTXt_SUPPORTED
  1448. /* Write a compressed text chunk */
  1449. void /* PRIVATE */
  1450. png_write_zTXt(png_structp png_ptr, png_const_charp key, png_const_charp text,
  1451.     png_size_t text_len, int compression)
  1452. {
  1453.    PNG_zTXt;
  1454.    png_size_t key_len;
  1455.    png_byte buf;
  1456.    png_charp new_key;
  1457.    compression_state comp;
  1458.  
  1459.    png_debug(1, "in png_write_zTXt");
  1460.  
  1461.    comp.num_output_ptr = 0;
  1462.    comp.max_output_ptr = 0;
  1463.    comp.output_ptr = NULL;
  1464.    comp.input = NULL;
  1465.    comp.input_len = 0;
  1466.  
  1467.    if ((key_len = png_check_keyword(png_ptr, key, &new_key)) == 0)
  1468.    {
  1469.       png_free(png_ptr, new_key);
  1470.       return;
  1471.    }
  1472.  
  1473.    if (text == NULL || *text == '\0' || compression==PNG_TEXT_COMPRESSION_NONE)
  1474.    {
  1475.       png_write_tEXt(png_ptr, new_key, text, (png_size_t)0);
  1476.       png_free(png_ptr, new_key);
  1477.       return;
  1478.    }
  1479.  
  1480.    text_len = png_strlen(text);
  1481.  
  1482.    /* Compute the compressed data; do it now for the length */
  1483.    text_len = png_text_compress(png_ptr, text, text_len, compression,
  1484.        &comp);
  1485.  
  1486.    /* Write start of chunk */
  1487.    png_write_chunk_start(png_ptr, png_zTXt,
  1488.        (png_uint_32)(key_len+text_len + 2));
  1489.  
  1490.    /* Write key */
  1491.    png_write_chunk_data(png_ptr, (png_bytep)new_key,
  1492.        (png_size_t)(key_len + 1));
  1493.  
  1494.    png_free(png_ptr, new_key);
  1495.  
  1496.    buf = (png_byte)compression;
  1497.  
  1498.    /* Write compression */
  1499.    png_write_chunk_data(png_ptr, &buf, (png_size_t)1);
  1500.  
  1501.    /* Write the compressed data */
  1502.    png_write_compressed_data_out(png_ptr, &comp);
  1503.  
  1504.    /* Close the chunk */
  1505.    png_write_chunk_end(png_ptr);
  1506. }
  1507. #endif
  1508.  
  1509. #ifdef PNG_WRITE_iTXt_SUPPORTED
  1510. /* Write an iTXt chunk */
  1511. void /* PRIVATE */
  1512. png_write_iTXt(png_structp png_ptr, int compression, png_const_charp key,
  1513.     png_const_charp lang, png_const_charp lang_key, png_const_charp text)
  1514. {
  1515.    PNG_iTXt;
  1516.    png_size_t lang_len, key_len, lang_key_len, text_len;
  1517.    png_charp new_lang;
  1518.    png_charp new_key = NULL;
  1519.    png_byte cbuf[2];
  1520.    compression_state comp;
  1521.  
  1522.    png_debug(1, "in png_write_iTXt");
  1523.  
  1524.    comp.num_output_ptr = 0;
  1525.    comp.max_output_ptr = 0;
  1526.    comp.output_ptr = NULL;
  1527.    comp.input = NULL;
  1528.  
  1529.    if ((key_len = png_check_keyword(png_ptr, key, &new_key)) == 0)
  1530.       return;
  1531.  
  1532.    if ((lang_len = png_check_keyword(png_ptr, lang, &new_lang)) == 0)
  1533.    {
  1534.       png_warning(png_ptr, "Empty language field in iTXt chunk");
  1535.       new_lang = NULL;
  1536.       lang_len = 0;
  1537.    }
  1538.  
  1539.    if (lang_key == NULL)
  1540.       lang_key_len = 0;
  1541.  
  1542.    else
  1543.       lang_key_len = png_strlen(lang_key);
  1544.  
  1545.    if (text == NULL)
  1546.       text_len = 0;
  1547.  
  1548.    else
  1549.       text_len = png_strlen(text);
  1550.  
  1551.    /* Compute the compressed data; do it now for the length */
  1552.    text_len = png_text_compress(png_ptr, text, text_len, compression - 2,
  1553.        &comp);
  1554.  
  1555.  
  1556.    /* Make sure we include the compression flag, the compression byte,
  1557.     * and the NULs after the key, lang, and lang_key parts
  1558.     */
  1559.  
  1560.    png_write_chunk_start(png_ptr, png_iTXt, (png_uint_32)(
  1561.         5 /* comp byte, comp flag, terminators for key, lang and lang_key */
  1562.         + key_len
  1563.         + lang_len
  1564.         + lang_key_len
  1565.         + text_len));
  1566.  
  1567.    /* We leave it to the application to meet PNG-1.0 requirements on the
  1568.     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
  1569.     * any non-Latin-1 characters except for NEWLINE.  ISO PNG will forbid them.
  1570.     * The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
  1571.     */
  1572.    png_write_chunk_data(png_ptr, (png_bytep)new_key, (png_size_t)(key_len + 1));
  1573.  
  1574.    /* Set the compression flag */
  1575.    if (compression == PNG_ITXT_COMPRESSION_NONE ||
  1576.        compression == PNG_TEXT_COMPRESSION_NONE)
  1577.       cbuf[0] = 0;
  1578.  
  1579.    else /* compression == PNG_ITXT_COMPRESSION_zTXt */
  1580.       cbuf[0] = 1;
  1581.  
  1582.    /* Set the compression method */
  1583.    cbuf[1] = 0;
  1584.  
  1585.    png_write_chunk_data(png_ptr, cbuf, (png_size_t)2);
  1586.  
  1587.    cbuf[0] = 0;
  1588.    png_write_chunk_data(png_ptr, (new_lang ? (png_const_bytep)new_lang : cbuf),
  1589.        (png_size_t)(lang_len + 1));
  1590.  
  1591.    png_write_chunk_data(png_ptr, (lang_key ? (png_const_bytep)lang_key : cbuf),
  1592.        (png_size_t)(lang_key_len + 1));
  1593.  
  1594.    png_write_compressed_data_out(png_ptr, &comp);
  1595.  
  1596.    png_write_chunk_end(png_ptr);
  1597.  
  1598.    png_free(png_ptr, new_key);
  1599.    png_free(png_ptr, new_lang);
  1600. }
  1601. #endif
  1602.  
  1603. #ifdef PNG_WRITE_oFFs_SUPPORTED
  1604. /* Write the oFFs chunk */
  1605. void /* PRIVATE */
  1606. png_write_oFFs(png_structp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
  1607.     int unit_type)
  1608. {
  1609.    PNG_oFFs;
  1610.    png_byte buf[9];
  1611.  
  1612.    png_debug(1, "in png_write_oFFs");
  1613.  
  1614.    if (unit_type >= PNG_OFFSET_LAST)
  1615.       png_warning(png_ptr, "Unrecognized unit type for oFFs chunk");
  1616.  
  1617.    png_save_int_32(buf, x_offset);
  1618.    png_save_int_32(buf + 4, y_offset);
  1619.    buf[8] = (png_byte)unit_type;
  1620.  
  1621.    png_write_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
  1622. }
  1623. #endif
  1624. #ifdef PNG_WRITE_pCAL_SUPPORTED
  1625. /* Write the pCAL chunk (described in the PNG extensions document) */
  1626. void /* PRIVATE */
  1627. png_write_pCAL(png_structp png_ptr, png_charp purpose, png_int_32 X0,
  1628.     png_int_32 X1, int type, int nparams, png_const_charp units,
  1629.     png_charpp params)
  1630. {
  1631.    PNG_pCAL;
  1632.    png_size_t purpose_len, units_len, total_len;
  1633.    png_uint_32p params_len;
  1634.    png_byte buf[10];
  1635.    png_charp new_purpose;
  1636.    int i;
  1637.  
  1638.    png_debug1(1, "in png_write_pCAL (%d parameters)", nparams);
  1639.  
  1640.    if (type >= PNG_EQUATION_LAST)
  1641.       png_warning(png_ptr, "Unrecognized equation type for pCAL chunk");
  1642.  
  1643.    purpose_len = png_check_keyword(png_ptr, purpose, &new_purpose) + 1;
  1644.    png_debug1(3, "pCAL purpose length = %d", (int)purpose_len);
  1645.    units_len = png_strlen(units) + (nparams == 0 ? 0 : 1);
  1646.    png_debug1(3, "pCAL units length = %d", (int)units_len);
  1647.    total_len = purpose_len + units_len + 10;
  1648.  
  1649.    params_len = (png_uint_32p)png_malloc(png_ptr,
  1650.        (png_alloc_size_t)(nparams * png_sizeof(png_uint_32)));
  1651.  
  1652.    /* Find the length of each parameter, making sure we don't count the
  1653.     * null terminator for the last parameter.
  1654.     */
  1655.    for (i = 0; i < nparams; i++)
  1656.    {
  1657.       params_len[i] = png_strlen(params[i]) + (i == nparams - 1 ? 0 : 1);
  1658.       png_debug2(3, "pCAL parameter %d length = %lu", i,
  1659.           (unsigned long)params_len[i]);
  1660.       total_len += (png_size_t)params_len[i];
  1661.    }
  1662.  
  1663.    png_debug1(3, "pCAL total length = %d", (int)total_len);
  1664.    png_write_chunk_start(png_ptr, png_pCAL, (png_uint_32)total_len);
  1665.    png_write_chunk_data(png_ptr, (png_const_bytep)new_purpose,
  1666.        (png_size_t)purpose_len);
  1667.    png_save_int_32(buf, X0);
  1668.    png_save_int_32(buf + 4, X1);
  1669.    buf[8] = (png_byte)type;
  1670.    buf[9] = (png_byte)nparams;
  1671.    png_write_chunk_data(png_ptr, buf, (png_size_t)10);
  1672.    png_write_chunk_data(png_ptr, (png_const_bytep)units, (png_size_t)units_len);
  1673.  
  1674.    png_free(png_ptr, new_purpose);
  1675.  
  1676.    for (i = 0; i < nparams; i++)
  1677.    {
  1678.       png_write_chunk_data(png_ptr, (png_const_bytep)params[i],
  1679.           (png_size_t)params_len[i]);
  1680.    }
  1681.  
  1682.    png_free(png_ptr, params_len);
  1683.    png_write_chunk_end(png_ptr);
  1684. }
  1685. #endif
  1686.  
  1687. #ifdef PNG_WRITE_sCAL_SUPPORTED
  1688. /* Write the sCAL chunk */
  1689. void /* PRIVATE */
  1690. png_write_sCAL_s(png_structp png_ptr, int unit, png_const_charp width,
  1691.     png_const_charp height)
  1692. {
  1693.    PNG_sCAL;
  1694.    png_byte buf[64];
  1695.    png_size_t wlen, hlen, total_len;
  1696.  
  1697.    png_debug(1, "in png_write_sCAL_s");
  1698.  
  1699.    wlen = png_strlen(width);
  1700.    hlen = png_strlen(height);
  1701.    total_len = wlen + hlen + 2;
  1702.  
  1703.    if (total_len > 64)
  1704.    {
  1705.       png_warning(png_ptr, "Can't write sCAL (buffer too small)");
  1706.       return;
  1707.    }
  1708.  
  1709.    buf[0] = (png_byte)unit;
  1710.    png_memcpy(buf + 1, width, wlen + 1);      /* Append the '\0' here */
  1711.    png_memcpy(buf + wlen + 2, height, hlen);  /* Do NOT append the '\0' here */
  1712.  
  1713.    png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
  1714.    png_write_chunk(png_ptr, png_sCAL, buf, total_len);
  1715. }
  1716. #endif
  1717.  
  1718. #ifdef PNG_WRITE_pHYs_SUPPORTED
  1719. /* Write the pHYs chunk */
  1720. void /* PRIVATE */
  1721. png_write_pHYs(png_structp png_ptr, png_uint_32 x_pixels_per_unit,
  1722.     png_uint_32 y_pixels_per_unit,
  1723.     int unit_type)
  1724. {
  1725.    PNG_pHYs;
  1726.    png_byte buf[9];
  1727.  
  1728.    png_debug(1, "in png_write_pHYs");
  1729.  
  1730.    if (unit_type >= PNG_RESOLUTION_LAST)
  1731.       png_warning(png_ptr, "Unrecognized unit type for pHYs chunk");
  1732.  
  1733.    png_save_uint_32(buf, x_pixels_per_unit);
  1734.    png_save_uint_32(buf + 4, y_pixels_per_unit);
  1735.    buf[8] = (png_byte)unit_type;
  1736.  
  1737.    png_write_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
  1738. }
  1739. #endif
  1740.  
  1741. #ifdef PNG_WRITE_tIME_SUPPORTED
  1742. /* Write the tIME chunk.  Use either png_convert_from_struct_tm()
  1743.  * or png_convert_from_time_t(), or fill in the structure yourself.
  1744.  */
  1745. void /* PRIVATE */
  1746. png_write_tIME(png_structp png_ptr, png_const_timep mod_time)
  1747. {
  1748.    PNG_tIME;
  1749.    png_byte buf[7];
  1750.  
  1751.    png_debug(1, "in png_write_tIME");
  1752.  
  1753.    if (mod_time->month  > 12 || mod_time->month  < 1 ||
  1754.        mod_time->day    > 31 || mod_time->day    < 1 ||
  1755.        mod_time->hour   > 23 || mod_time->second > 60)
  1756.    {
  1757.       png_warning(png_ptr, "Invalid time specified for tIME chunk");
  1758.       return;
  1759.    }
  1760.  
  1761.    png_save_uint_16(buf, mod_time->year);
  1762.    buf[2] = mod_time->month;
  1763.    buf[3] = mod_time->day;
  1764.    buf[4] = mod_time->hour;
  1765.    buf[5] = mod_time->minute;
  1766.    buf[6] = mod_time->second;
  1767.  
  1768.    png_write_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
  1769. }
  1770. #endif
  1771.  
  1772. /* Initializes the row writing capability of libpng */
  1773. void /* PRIVATE */
  1774. png_write_start_row(png_structp png_ptr)
  1775. {
  1776. #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  1777.    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
  1778.  
  1779.    /* Start of interlace block */
  1780.    int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
  1781.  
  1782.    /* Offset to next interlace block */
  1783.    int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
  1784.  
  1785.    /* Start of interlace block in the y direction */
  1786.    int png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
  1787.  
  1788.    /* Offset to next interlace block in the y direction */
  1789.    int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
  1790. #endif
  1791.  
  1792.    png_size_t buf_size;
  1793.  
  1794.    png_debug(1, "in png_write_start_row");
  1795.  
  1796.    buf_size = (png_size_t)(PNG_ROWBYTES(
  1797.        png_ptr->usr_channels*png_ptr->usr_bit_depth, png_ptr->width) + 1);
  1798.  
  1799.    /* Set up row buffer */
  1800.    png_ptr->row_buf = (png_bytep)png_malloc(png_ptr,
  1801.        (png_alloc_size_t)buf_size);
  1802.  
  1803.    png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
  1804.  
  1805. #ifdef PNG_WRITE_FILTER_SUPPORTED
  1806.    /* Set up filtering buffer, if using this filter */
  1807.    if (png_ptr->do_filter & PNG_FILTER_SUB)
  1808.    {
  1809.       png_ptr->sub_row = (png_bytep)png_malloc(png_ptr, png_ptr->rowbytes + 1);
  1810.  
  1811.       png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
  1812.    }
  1813.  
  1814.    /* We only need to keep the previous row if we are using one of these. */
  1815.    if (png_ptr->do_filter & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH))
  1816.    {
  1817.       /* Set up previous row buffer */
  1818.       png_ptr->prev_row = (png_bytep)png_calloc(png_ptr,
  1819.           (png_alloc_size_t)buf_size);
  1820.  
  1821.       if (png_ptr->do_filter & PNG_FILTER_UP)
  1822.       {
  1823.          png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
  1824.             png_ptr->rowbytes + 1);
  1825.  
  1826.          png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
  1827.       }
  1828.  
  1829.       if (png_ptr->do_filter & PNG_FILTER_AVG)
  1830.       {
  1831.          png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
  1832.              png_ptr->rowbytes + 1);
  1833.  
  1834.          png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
  1835.       }
  1836.  
  1837.       if (png_ptr->do_filter & PNG_FILTER_PAETH)
  1838.       {
  1839.          png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
  1840.              png_ptr->rowbytes + 1);
  1841.  
  1842.          png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
  1843.       }
  1844.    }
  1845. #endif /* PNG_WRITE_FILTER_SUPPORTED */
  1846.  
  1847. #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  1848.    /* If interlaced, we need to set up width and height of pass */
  1849.    if (png_ptr->interlaced)
  1850.    {
  1851.       if (!(png_ptr->transformations & PNG_INTERLACE))
  1852.       {
  1853.          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
  1854.              png_pass_ystart[0]) / png_pass_yinc[0];
  1855.  
  1856.          png_ptr->usr_width = (png_ptr->width + png_pass_inc[0] - 1 -
  1857.              png_pass_start[0]) / png_pass_inc[0];
  1858.       }
  1859.  
  1860.       else
  1861.       {
  1862.          png_ptr->num_rows = png_ptr->height;
  1863.          png_ptr->usr_width = png_ptr->width;
  1864.       }
  1865.    }
  1866.  
  1867.    else
  1868. #endif
  1869.    {
  1870.       png_ptr->num_rows = png_ptr->height;
  1871.       png_ptr->usr_width = png_ptr->width;
  1872.    }
  1873.  
  1874.    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
  1875.    png_ptr->zstream.next_out = png_ptr->zbuf;
  1876. }
  1877.  
  1878. /* Internal use only.  Called when finished processing a row of data. */
  1879. void /* PRIVATE */
  1880. png_write_finish_row(png_structp png_ptr)
  1881. {
  1882. #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  1883.    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
  1884.  
  1885.    /* Start of interlace block */
  1886.    int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
  1887.  
  1888.    /* Offset to next interlace block */
  1889.    int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
  1890.  
  1891.    /* Start of interlace block in the y direction */
  1892.    int png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
  1893.  
  1894.    /* Offset to next interlace block in the y direction */
  1895.    int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
  1896. #endif
  1897.  
  1898.    int ret;
  1899.  
  1900.    png_debug(1, "in png_write_finish_row");
  1901.  
  1902.    /* Next row */
  1903.    png_ptr->row_number++;
  1904.  
  1905.    /* See if we are done */
  1906.    if (png_ptr->row_number < png_ptr->num_rows)
  1907.       return;
  1908.  
  1909. #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  1910.    /* If interlaced, go to next pass */
  1911.    if (png_ptr->interlaced)
  1912.    {
  1913.       png_ptr->row_number = 0;
  1914.       if (png_ptr->transformations & PNG_INTERLACE)
  1915.       {
  1916.          png_ptr->pass++;
  1917.       }
  1918.  
  1919.       else
  1920.       {
  1921.          /* Loop until we find a non-zero width or height pass */
  1922.          do
  1923.          {
  1924.             png_ptr->pass++;
  1925.  
  1926.             if (png_ptr->pass >= 7)
  1927.                break;
  1928.  
  1929.             png_ptr->usr_width = (png_ptr->width +
  1930.                 png_pass_inc[png_ptr->pass] - 1 -
  1931.                 png_pass_start[png_ptr->pass]) /
  1932.                 png_pass_inc[png_ptr->pass];
  1933.  
  1934.             png_ptr->num_rows = (png_ptr->height +
  1935.                 png_pass_yinc[png_ptr->pass] - 1 -
  1936.                 png_pass_ystart[png_ptr->pass]) /
  1937.                 png_pass_yinc[png_ptr->pass];
  1938.  
  1939.             if (png_ptr->transformations & PNG_INTERLACE)
  1940.                break;
  1941.  
  1942.          } while (png_ptr->usr_width == 0 || png_ptr->num_rows == 0);
  1943.  
  1944.       }
  1945.  
  1946.       /* Reset the row above the image for the next pass */
  1947.       if (png_ptr->pass < 7)
  1948.       {
  1949.          if (png_ptr->prev_row != NULL)
  1950.             png_memset(png_ptr->prev_row, 0,
  1951.                 (png_size_t)(PNG_ROWBYTES(png_ptr->usr_channels*
  1952.                 png_ptr->usr_bit_depth, png_ptr->width)) + 1);
  1953.  
  1954.          return;
  1955.       }
  1956.    }
  1957. #endif
  1958.  
  1959.    /* If we get here, we've just written the last row, so we need
  1960.       to flush the compressor */
  1961.    do
  1962.    {
  1963.       /* Tell the compressor we are done */
  1964.       ret = deflate(&png_ptr->zstream, Z_FINISH);
  1965.  
  1966.       /* Check for an error */
  1967.       if (ret == Z_OK)
  1968.       {
  1969.          /* Check to see if we need more room */
  1970.          if (!(png_ptr->zstream.avail_out))
  1971.          {
  1972.             png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
  1973.             png_ptr->zstream.next_out = png_ptr->zbuf;
  1974.             png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
  1975.          }
  1976.       }
  1977.  
  1978.       else if (ret != Z_STREAM_END)
  1979.       {
  1980.          if (png_ptr->zstream.msg != NULL)
  1981.             png_error(png_ptr, png_ptr->zstream.msg);
  1982.  
  1983.          else
  1984.             png_error(png_ptr, "zlib error");
  1985.       }
  1986.    } while (ret != Z_STREAM_END);
  1987.  
  1988.    /* Write any extra space */
  1989.    if (png_ptr->zstream.avail_out < png_ptr->zbuf_size)
  1990.    {
  1991.       png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size -
  1992.           png_ptr->zstream.avail_out);
  1993.    }
  1994.  
  1995.    deflateReset(&png_ptr->zstream);
  1996.    png_ptr->zstream.data_type = Z_BINARY;
  1997. }
  1998.  
  1999. #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  2000. /* Pick out the correct pixels for the interlace pass.
  2001.  * The basic idea here is to go through the row with a source
  2002.  * pointer and a destination pointer (sp and dp), and copy the
  2003.  * correct pixels for the pass.  As the row gets compacted,
  2004.  * sp will always be >= dp, so we should never overwrite anything.
  2005.  * See the default: case for the easiest code to understand.
  2006.  */
  2007. void /* PRIVATE */
  2008. png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
  2009. {
  2010.    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
  2011.  
  2012.    /* Start of interlace block */
  2013.    int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
  2014.  
  2015.    /* Offset to next interlace block */
  2016.    int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
  2017.  
  2018.    png_debug(1, "in png_do_write_interlace");
  2019.  
  2020.    /* We don't have to do anything on the last pass (6) */
  2021.    if (pass < 6)
  2022.    {
  2023.       /* Each pixel depth is handled separately */
  2024.       switch (row_info->pixel_depth)
  2025.       {
  2026.          case 1:
  2027.          {
  2028.             png_bytep sp;
  2029.             png_bytep dp;
  2030.             int shift;
  2031.             int d;
  2032.             int value;
  2033.             png_uint_32 i;
  2034.             png_uint_32 row_width = row_info->width;
  2035.  
  2036.             dp = row;
  2037.             d = 0;
  2038.             shift = 7;
  2039.  
  2040.             for (i = png_pass_start[pass]; i < row_width;
  2041.                i += png_pass_inc[pass])
  2042.             {
  2043.                sp = row + (png_size_t)(i >> 3);
  2044.                value = (int)(*sp >> (7 - (int)(i & 0x07))) & 0x01;
  2045.                d |= (value << shift);
  2046.  
  2047.                if (shift == 0)
  2048.                {
  2049.                   shift = 7;
  2050.                   *dp++ = (png_byte)d;
  2051.                   d = 0;
  2052.                }
  2053.  
  2054.                else
  2055.                   shift--;
  2056.  
  2057.             }
  2058.             if (shift != 7)
  2059.                *dp = (png_byte)d;
  2060.  
  2061.             break;
  2062.          }
  2063.  
  2064.          case 2:
  2065.          {
  2066.             png_bytep sp;
  2067.             png_bytep dp;
  2068.             int shift;
  2069.             int d;
  2070.             int value;
  2071.             png_uint_32 i;
  2072.             png_uint_32 row_width = row_info->width;
  2073.  
  2074.             dp = row;
  2075.             shift = 6;
  2076.             d = 0;
  2077.  
  2078.             for (i = png_pass_start[pass]; i < row_width;
  2079.                i += png_pass_inc[pass])
  2080.             {
  2081.                sp = row + (png_size_t)(i >> 2);
  2082.                value = (*sp >> ((3 - (int)(i & 0x03)) << 1)) & 0x03;
  2083.                d |= (value << shift);
  2084.  
  2085.                if (shift == 0)
  2086.                {
  2087.                   shift = 6;
  2088.                   *dp++ = (png_byte)d;
  2089.                   d = 0;
  2090.                }
  2091.  
  2092.                else
  2093.                   shift -= 2;
  2094.             }
  2095.             if (shift != 6)
  2096.                *dp = (png_byte)d;
  2097.  
  2098.             break;
  2099.          }
  2100.  
  2101.          case 4:
  2102.          {
  2103.             png_bytep sp;
  2104.             png_bytep dp;
  2105.             int shift;
  2106.             int d;
  2107.             int value;
  2108.             png_uint_32 i;
  2109.             png_uint_32 row_width = row_info->width;
  2110.  
  2111.             dp = row;
  2112.             shift = 4;
  2113.             d = 0;
  2114.             for (i = png_pass_start[pass]; i < row_width;
  2115.                 i += png_pass_inc[pass])
  2116.             {
  2117.                sp = row + (png_size_t)(i >> 1);
  2118.                value = (*sp >> ((1 - (int)(i & 0x01)) << 2)) & 0x0f;
  2119.                d |= (value << shift);
  2120.  
  2121.                if (shift == 0)
  2122.                {
  2123.                   shift = 4;
  2124.                   *dp++ = (png_byte)d;
  2125.                   d = 0;
  2126.                }
  2127.  
  2128.                else
  2129.                   shift -= 4;
  2130.             }
  2131.             if (shift != 4)
  2132.                *dp = (png_byte)d;
  2133.  
  2134.             break;
  2135.          }
  2136.  
  2137.          default:
  2138.          {
  2139.             png_bytep sp;
  2140.             png_bytep dp;
  2141.             png_uint_32 i;
  2142.             png_uint_32 row_width = row_info->width;
  2143.             png_size_t pixel_bytes;
  2144.  
  2145.             /* Start at the beginning */
  2146.             dp = row;
  2147.  
  2148.             /* Find out how many bytes each pixel takes up */
  2149.             pixel_bytes = (row_info->pixel_depth >> 3);
  2150.  
  2151.             /* Loop through the row, only looking at the pixels that matter */
  2152.             for (i = png_pass_start[pass]; i < row_width;
  2153.                i += png_pass_inc[pass])
  2154.             {
  2155.                /* Find out where the original pixel is */
  2156.                sp = row + (png_size_t)i * pixel_bytes;
  2157.  
  2158.                /* Move the pixel */
  2159.                if (dp != sp)
  2160.                   png_memcpy(dp, sp, pixel_bytes);
  2161.  
  2162.                /* Next pixel */
  2163.                dp += pixel_bytes;
  2164.             }
  2165.             break;
  2166.          }
  2167.       }
  2168.       /* Set new row width */
  2169.       row_info->width = (row_info->width +
  2170.           png_pass_inc[pass] - 1 -
  2171.           png_pass_start[pass]) /
  2172.           png_pass_inc[pass];
  2173.  
  2174.       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
  2175.           row_info->width);
  2176.    }
  2177. }
  2178. #endif
  2179.  
  2180. /* This filters the row, chooses which filter to use, if it has not already
  2181.  * been specified by the application, and then writes the row out with the
  2182.  * chosen filter.
  2183.  */
  2184. #define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
  2185. #define PNG_HISHIFT 10
  2186. #define PNG_LOMASK ((png_uint_32)0xffffL)
  2187. #define PNG_HIMASK ((png_uint_32)(~PNG_LOMASK >> PNG_HISHIFT))
  2188. void /* PRIVATE */
  2189. png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
  2190. {
  2191.    png_bytep best_row;
  2192. #ifdef PNG_WRITE_FILTER_SUPPORTED
  2193.    png_bytep prev_row, row_buf;
  2194.    png_uint_32 mins, bpp;
  2195.    png_byte filter_to_do = png_ptr->do_filter;
  2196.    png_size_t row_bytes = row_info->rowbytes;
  2197. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2198.    int num_p_filters = (int)png_ptr->num_prev_filters;
  2199. #endif
  2200.  
  2201.    png_debug(1, "in png_write_find_filter");
  2202.  
  2203. #ifndef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2204.   if (png_ptr->row_number == 0 && filter_to_do == PNG_ALL_FILTERS)
  2205.   {
  2206.      /* These will never be selected so we need not test them. */
  2207.      filter_to_do &= ~(PNG_FILTER_UP | PNG_FILTER_PAETH);
  2208.   }
  2209. #endif
  2210.  
  2211.    /* Find out how many bytes offset each pixel is */
  2212.    bpp = (row_info->pixel_depth + 7) >> 3;
  2213.  
  2214.    prev_row = png_ptr->prev_row;
  2215. #endif
  2216.    best_row = png_ptr->row_buf;
  2217. #ifdef PNG_WRITE_FILTER_SUPPORTED
  2218.    row_buf = best_row;
  2219.    mins = PNG_MAXSUM;
  2220.  
  2221.    /* The prediction method we use is to find which method provides the
  2222.     * smallest value when summing the absolute values of the distances
  2223.     * from zero, using anything >= 128 as negative numbers.  This is known
  2224.     * as the "minimum sum of absolute differences" heuristic.  Other
  2225.     * heuristics are the "weighted minimum sum of absolute differences"
  2226.     * (experimental and can in theory improve compression), and the "zlib
  2227.     * predictive" method (not implemented yet), which does test compressions
  2228.     * of lines using different filter methods, and then chooses the
  2229.     * (series of) filter(s) that give minimum compressed data size (VERY
  2230.     * computationally expensive).
  2231.     *
  2232.     * GRR 980525:  consider also
  2233.     *
  2234.     *   (1) minimum sum of absolute differences from running average (i.e.,
  2235.     *       keep running sum of non-absolute differences & count of bytes)
  2236.     *       [track dispersion, too?  restart average if dispersion too large?]
  2237.     *
  2238.     *  (1b) minimum sum of absolute differences from sliding average, probably
  2239.     *       with window size <= deflate window (usually 32K)
  2240.     *
  2241.     *   (2) minimum sum of squared differences from zero or running average
  2242.     *       (i.e., ~ root-mean-square approach)
  2243.     */
  2244.  
  2245.  
  2246.    /* We don't need to test the 'no filter' case if this is the only filter
  2247.     * that has been chosen, as it doesn't actually do anything to the data.
  2248.     */
  2249.    if ((filter_to_do & PNG_FILTER_NONE) && filter_to_do != PNG_FILTER_NONE)
  2250.    {
  2251.       png_bytep rp;
  2252.       png_uint_32 sum = 0;
  2253.       png_size_t i;
  2254.       int v;
  2255.  
  2256.       for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
  2257.       {
  2258.          v = *rp;
  2259.          sum += (v < 128) ? v : 256 - v;
  2260.       }
  2261.  
  2262. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2263.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2264.       {
  2265.          png_uint_32 sumhi, sumlo;
  2266.          int j;
  2267.          sumlo = sum & PNG_LOMASK;
  2268.          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK; /* Gives us some footroom */
  2269.  
  2270.          /* Reduce the sum if we match any of the previous rows */
  2271.          for (j = 0; j < num_p_filters; j++)
  2272.          {
  2273.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
  2274.             {
  2275.                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
  2276.                    PNG_WEIGHT_SHIFT;
  2277.  
  2278.                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
  2279.                    PNG_WEIGHT_SHIFT;
  2280.             }
  2281.          }
  2282.  
  2283.          /* Factor in the cost of this filter (this is here for completeness,
  2284.           * but it makes no sense to have a "cost" for the NONE filter, as
  2285.           * it has the minimum possible computational cost - none).
  2286.           */
  2287.          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
  2288.              PNG_COST_SHIFT;
  2289.  
  2290.          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
  2291.              PNG_COST_SHIFT;
  2292.  
  2293.          if (sumhi > PNG_HIMASK)
  2294.             sum = PNG_MAXSUM;
  2295.  
  2296.          else
  2297.             sum = (sumhi << PNG_HISHIFT) + sumlo;
  2298.       }
  2299. #endif
  2300.       mins = sum;
  2301.    }
  2302.  
  2303.    /* Sub filter */
  2304.    if (filter_to_do == PNG_FILTER_SUB)
  2305.    /* It's the only filter so no testing is needed */
  2306.    {
  2307.       png_bytep rp, lp, dp;
  2308.       png_size_t i;
  2309.  
  2310.       for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
  2311.            i++, rp++, dp++)
  2312.       {
  2313.          *dp = *rp;
  2314.       }
  2315.  
  2316.       for (lp = row_buf + 1; i < row_bytes;
  2317.          i++, rp++, lp++, dp++)
  2318.       {
  2319.          *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
  2320.       }
  2321.  
  2322.       best_row = png_ptr->sub_row;
  2323.    }
  2324.  
  2325.    else if (filter_to_do & PNG_FILTER_SUB)
  2326.    {
  2327.       png_bytep rp, dp, lp;
  2328.       png_uint_32 sum = 0, lmins = mins;
  2329.       png_size_t i;
  2330.       int v;
  2331.  
  2332. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2333.       /* We temporarily increase the "minimum sum" by the factor we
  2334.        * would reduce the sum of this filter, so that we can do the
  2335.        * early exit comparison without scaling the sum each time.
  2336.        */
  2337.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2338.       {
  2339.          int j;
  2340.          png_uint_32 lmhi, lmlo;
  2341.          lmlo = lmins & PNG_LOMASK;
  2342.          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
  2343.  
  2344.          for (j = 0; j < num_p_filters; j++)
  2345.          {
  2346.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
  2347.             {
  2348.                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
  2349.                    PNG_WEIGHT_SHIFT;
  2350.  
  2351.                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
  2352.                    PNG_WEIGHT_SHIFT;
  2353.             }
  2354.          }
  2355.  
  2356.          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
  2357.              PNG_COST_SHIFT;
  2358.  
  2359.          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
  2360.              PNG_COST_SHIFT;
  2361.  
  2362.          if (lmhi > PNG_HIMASK)
  2363.             lmins = PNG_MAXSUM;
  2364.  
  2365.          else
  2366.             lmins = (lmhi << PNG_HISHIFT) + lmlo;
  2367.       }
  2368. #endif
  2369.  
  2370.       for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
  2371.            i++, rp++, dp++)
  2372.       {
  2373.          v = *dp = *rp;
  2374.  
  2375.          sum += (v < 128) ? v : 256 - v;
  2376.       }
  2377.  
  2378.       for (lp = row_buf + 1; i < row_bytes;
  2379.          i++, rp++, lp++, dp++)
  2380.       {
  2381.          v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
  2382.  
  2383.          sum += (v < 128) ? v : 256 - v;
  2384.  
  2385.          if (sum > lmins)  /* We are already worse, don't continue. */
  2386.             break;
  2387.       }
  2388.  
  2389. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2390.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2391.       {
  2392.          int j;
  2393.          png_uint_32 sumhi, sumlo;
  2394.          sumlo = sum & PNG_LOMASK;
  2395.          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
  2396.  
  2397.          for (j = 0; j < num_p_filters; j++)
  2398.          {
  2399.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
  2400.             {
  2401.                sumlo = (sumlo * png_ptr->inv_filter_weights[j]) >>
  2402.                    PNG_WEIGHT_SHIFT;
  2403.  
  2404.                sumhi = (sumhi * png_ptr->inv_filter_weights[j]) >>
  2405.                    PNG_WEIGHT_SHIFT;
  2406.             }
  2407.          }
  2408.  
  2409.          sumlo = (sumlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
  2410.              PNG_COST_SHIFT;
  2411.  
  2412.          sumhi = (sumhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
  2413.              PNG_COST_SHIFT;
  2414.  
  2415.          if (sumhi > PNG_HIMASK)
  2416.             sum = PNG_MAXSUM;
  2417.  
  2418.          else
  2419.             sum = (sumhi << PNG_HISHIFT) + sumlo;
  2420.       }
  2421. #endif
  2422.  
  2423.       if (sum < mins)
  2424.       {
  2425.          mins = sum;
  2426.          best_row = png_ptr->sub_row;
  2427.       }
  2428.    }
  2429.  
  2430.    /* Up filter */
  2431.    if (filter_to_do == PNG_FILTER_UP)
  2432.    {
  2433.       png_bytep rp, dp, pp;
  2434.       png_size_t i;
  2435.  
  2436.       for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
  2437.           pp = prev_row + 1; i < row_bytes;
  2438.           i++, rp++, pp++, dp++)
  2439.       {
  2440.          *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
  2441.       }
  2442.  
  2443.       best_row = png_ptr->up_row;
  2444.    }
  2445.  
  2446.    else if (filter_to_do & PNG_FILTER_UP)
  2447.    {
  2448.       png_bytep rp, dp, pp;
  2449.       png_uint_32 sum = 0, lmins = mins;
  2450.       png_size_t i;
  2451.       int v;
  2452.  
  2453.  
  2454. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2455.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2456.       {
  2457.          int j;
  2458.          png_uint_32 lmhi, lmlo;
  2459.          lmlo = lmins & PNG_LOMASK;
  2460.          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
  2461.  
  2462.          for (j = 0; j < num_p_filters; j++)
  2463.          {
  2464.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
  2465.             {
  2466.                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
  2467.                    PNG_WEIGHT_SHIFT;
  2468.  
  2469.                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
  2470.                    PNG_WEIGHT_SHIFT;
  2471.             }
  2472.          }
  2473.  
  2474.          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
  2475.              PNG_COST_SHIFT;
  2476.  
  2477.          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
  2478.              PNG_COST_SHIFT;
  2479.  
  2480.          if (lmhi > PNG_HIMASK)
  2481.             lmins = PNG_MAXSUM;
  2482.  
  2483.          else
  2484.             lmins = (lmhi << PNG_HISHIFT) + lmlo;
  2485.       }
  2486. #endif
  2487.  
  2488.       for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
  2489.           pp = prev_row + 1; i < row_bytes; i++)
  2490.       {
  2491.          v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
  2492.  
  2493.          sum += (v < 128) ? v : 256 - v;
  2494.  
  2495.          if (sum > lmins)  /* We are already worse, don't continue. */
  2496.             break;
  2497.       }
  2498.  
  2499. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2500.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2501.       {
  2502.          int j;
  2503.          png_uint_32 sumhi, sumlo;
  2504.          sumlo = sum & PNG_LOMASK;
  2505.          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
  2506.  
  2507.          for (j = 0; j < num_p_filters; j++)
  2508.          {
  2509.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
  2510.             {
  2511.                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
  2512.                    PNG_WEIGHT_SHIFT;
  2513.  
  2514.                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
  2515.                    PNG_WEIGHT_SHIFT;
  2516.             }
  2517.          }
  2518.  
  2519.          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
  2520.              PNG_COST_SHIFT;
  2521.  
  2522.          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
  2523.              PNG_COST_SHIFT;
  2524.  
  2525.          if (sumhi > PNG_HIMASK)
  2526.             sum = PNG_MAXSUM;
  2527.  
  2528.          else
  2529.             sum = (sumhi << PNG_HISHIFT) + sumlo;
  2530.       }
  2531. #endif
  2532.  
  2533.       if (sum < mins)
  2534.       {
  2535.          mins = sum;
  2536.          best_row = png_ptr->up_row;
  2537.       }
  2538.    }
  2539.  
  2540.    /* Avg filter */
  2541.    if (filter_to_do == PNG_FILTER_AVG)
  2542.    {
  2543.       png_bytep rp, dp, pp, lp;
  2544.       png_uint_32 i;
  2545.  
  2546.       for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
  2547.            pp = prev_row + 1; i < bpp; i++)
  2548.       {
  2549.          *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
  2550.       }
  2551.  
  2552.       for (lp = row_buf + 1; i < row_bytes; i++)
  2553.       {
  2554.          *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
  2555.                  & 0xff);
  2556.       }
  2557.       best_row = png_ptr->avg_row;
  2558.    }
  2559.  
  2560.    else if (filter_to_do & PNG_FILTER_AVG)
  2561.    {
  2562.       png_bytep rp, dp, pp, lp;
  2563.       png_uint_32 sum = 0, lmins = mins;
  2564.       png_size_t i;
  2565.       int v;
  2566.  
  2567. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2568.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2569.       {
  2570.          int j;
  2571.          png_uint_32 lmhi, lmlo;
  2572.          lmlo = lmins & PNG_LOMASK;
  2573.          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
  2574.  
  2575.          for (j = 0; j < num_p_filters; j++)
  2576.          {
  2577.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
  2578.             {
  2579.                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
  2580.                    PNG_WEIGHT_SHIFT;
  2581.  
  2582.                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
  2583.                    PNG_WEIGHT_SHIFT;
  2584.             }
  2585.          }
  2586.  
  2587.          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
  2588.              PNG_COST_SHIFT;
  2589.  
  2590.          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
  2591.              PNG_COST_SHIFT;
  2592.  
  2593.          if (lmhi > PNG_HIMASK)
  2594.             lmins = PNG_MAXSUM;
  2595.  
  2596.          else
  2597.             lmins = (lmhi << PNG_HISHIFT) + lmlo;
  2598.       }
  2599. #endif
  2600.  
  2601.       for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
  2602.            pp = prev_row + 1; i < bpp; i++)
  2603.       {
  2604.          v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
  2605.  
  2606.          sum += (v < 128) ? v : 256 - v;
  2607.       }
  2608.  
  2609.       for (lp = row_buf + 1; i < row_bytes; i++)
  2610.       {
  2611.          v = *dp++ =
  2612.              (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2)) & 0xff);
  2613.  
  2614.          sum += (v < 128) ? v : 256 - v;
  2615.  
  2616.          if (sum > lmins)  /* We are already worse, don't continue. */
  2617.             break;
  2618.       }
  2619.  
  2620. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2621.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2622.       {
  2623.          int j;
  2624.          png_uint_32 sumhi, sumlo;
  2625.          sumlo = sum & PNG_LOMASK;
  2626.          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
  2627.  
  2628.          for (j = 0; j < num_p_filters; j++)
  2629.          {
  2630.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
  2631.             {
  2632.                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
  2633.                    PNG_WEIGHT_SHIFT;
  2634.  
  2635.                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
  2636.                    PNG_WEIGHT_SHIFT;
  2637.             }
  2638.          }
  2639.  
  2640.          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
  2641.              PNG_COST_SHIFT;
  2642.  
  2643.          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
  2644.              PNG_COST_SHIFT;
  2645.  
  2646.          if (sumhi > PNG_HIMASK)
  2647.             sum = PNG_MAXSUM;
  2648.  
  2649.          else
  2650.             sum = (sumhi << PNG_HISHIFT) + sumlo;
  2651.       }
  2652. #endif
  2653.  
  2654.       if (sum < mins)
  2655.       {
  2656.          mins = sum;
  2657.          best_row = png_ptr->avg_row;
  2658.       }
  2659.    }
  2660.  
  2661.    /* Paeth filter */
  2662.    if (filter_to_do == PNG_FILTER_PAETH)
  2663.    {
  2664.       png_bytep rp, dp, pp, cp, lp;
  2665.       png_size_t i;
  2666.  
  2667.       for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
  2668.           pp = prev_row + 1; i < bpp; i++)
  2669.       {
  2670.          *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
  2671.       }
  2672.  
  2673.       for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
  2674.       {
  2675.          int a, b, c, pa, pb, pc, p;
  2676.  
  2677.          b = *pp++;
  2678.          c = *cp++;
  2679.          a = *lp++;
  2680.  
  2681.          p = b - c;
  2682.          pc = a - c;
  2683.  
  2684. #ifdef PNG_USE_ABS
  2685.          pa = abs(p);
  2686.          pb = abs(pc);
  2687.          pc = abs(p + pc);
  2688. #else
  2689.          pa = p < 0 ? -p : p;
  2690.          pb = pc < 0 ? -pc : pc;
  2691.          pc = (p + pc) < 0 ? -(p + pc) : p + pc;
  2692. #endif
  2693.  
  2694.          p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
  2695.  
  2696.          *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
  2697.       }
  2698.       best_row = png_ptr->paeth_row;
  2699.    }
  2700.  
  2701.    else if (filter_to_do & PNG_FILTER_PAETH)
  2702.    {
  2703.       png_bytep rp, dp, pp, cp, lp;
  2704.       png_uint_32 sum = 0, lmins = mins;
  2705.       png_size_t i;
  2706.       int v;
  2707.  
  2708. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2709.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2710.       {
  2711.          int j;
  2712.          png_uint_32 lmhi, lmlo;
  2713.          lmlo = lmins & PNG_LOMASK;
  2714.          lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
  2715.  
  2716.          for (j = 0; j < num_p_filters; j++)
  2717.          {
  2718.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
  2719.             {
  2720.                lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
  2721.                    PNG_WEIGHT_SHIFT;
  2722.  
  2723.                lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
  2724.                    PNG_WEIGHT_SHIFT;
  2725.             }
  2726.          }
  2727.  
  2728.          lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
  2729.              PNG_COST_SHIFT;
  2730.  
  2731.          lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
  2732.              PNG_COST_SHIFT;
  2733.  
  2734.          if (lmhi > PNG_HIMASK)
  2735.             lmins = PNG_MAXSUM;
  2736.  
  2737.          else
  2738.             lmins = (lmhi << PNG_HISHIFT) + lmlo;
  2739.       }
  2740. #endif
  2741.  
  2742.       for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
  2743.           pp = prev_row + 1; i < bpp; i++)
  2744.       {
  2745.          v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
  2746.  
  2747.          sum += (v < 128) ? v : 256 - v;
  2748.       }
  2749.  
  2750.       for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
  2751.       {
  2752.          int a, b, c, pa, pb, pc, p;
  2753.  
  2754.          b = *pp++;
  2755.          c = *cp++;
  2756.          a = *lp++;
  2757.  
  2758. #ifndef PNG_SLOW_PAETH
  2759.          p = b - c;
  2760.          pc = a - c;
  2761. #ifdef PNG_USE_ABS
  2762.          pa = abs(p);
  2763.          pb = abs(pc);
  2764.          pc = abs(p + pc);
  2765. #else
  2766.          pa = p < 0 ? -p : p;
  2767.          pb = pc < 0 ? -pc : pc;
  2768.          pc = (p + pc) < 0 ? -(p + pc) : p + pc;
  2769. #endif
  2770.          p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
  2771. #else /* PNG_SLOW_PAETH */
  2772.          p = a + b - c;
  2773.          pa = abs(p - a);
  2774.          pb = abs(p - b);
  2775.          pc = abs(p - c);
  2776.  
  2777.          if (pa <= pb && pa <= pc)
  2778.             p = a;
  2779.  
  2780.          else if (pb <= pc)
  2781.             p = b;
  2782.  
  2783.          else
  2784.             p = c;
  2785. #endif /* PNG_SLOW_PAETH */
  2786.  
  2787.          v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
  2788.  
  2789.          sum += (v < 128) ? v : 256 - v;
  2790.  
  2791.          if (sum > lmins)  /* We are already worse, don't continue. */
  2792.             break;
  2793.       }
  2794.  
  2795. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2796.       if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
  2797.       {
  2798.          int j;
  2799.          png_uint_32 sumhi, sumlo;
  2800.          sumlo = sum & PNG_LOMASK;
  2801.          sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
  2802.  
  2803.          for (j = 0; j < num_p_filters; j++)
  2804.          {
  2805.             if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
  2806.             {
  2807.                sumlo = (sumlo * png_ptr->filter_weights[j]) >>
  2808.                    PNG_WEIGHT_SHIFT;
  2809.  
  2810.                sumhi = (sumhi * png_ptr->filter_weights[j]) >>
  2811.                    PNG_WEIGHT_SHIFT;
  2812.             }
  2813.          }
  2814.  
  2815.          sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
  2816.              PNG_COST_SHIFT;
  2817.  
  2818.          sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
  2819.              PNG_COST_SHIFT;
  2820.  
  2821.          if (sumhi > PNG_HIMASK)
  2822.             sum = PNG_MAXSUM;
  2823.  
  2824.          else
  2825.             sum = (sumhi << PNG_HISHIFT) + sumlo;
  2826.       }
  2827. #endif
  2828.  
  2829.       if (sum < mins)
  2830.       {
  2831.          best_row = png_ptr->paeth_row;
  2832.       }
  2833.    }
  2834. #endif /* PNG_WRITE_FILTER_SUPPORTED */
  2835.    /* Do the actual writing of the filtered row data from the chosen filter. */
  2836.  
  2837.    png_write_filtered_row(png_ptr, best_row);
  2838.  
  2839. #ifdef PNG_WRITE_FILTER_SUPPORTED
  2840. #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  2841.    /* Save the type of filter we picked this time for future calculations */
  2842.    if (png_ptr->num_prev_filters > 0)
  2843.    {
  2844.       int j;
  2845.  
  2846.       for (j = 1; j < num_p_filters; j++)
  2847.       {
  2848.          png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
  2849.       }
  2850.  
  2851.       png_ptr->prev_filters[j] = best_row[0];
  2852.    }
  2853. #endif
  2854. #endif /* PNG_WRITE_FILTER_SUPPORTED */
  2855. }
  2856.  
  2857.  
  2858. /* Do the actual writing of a previously filtered row. */
  2859. void /* PRIVATE */
  2860. png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row)
  2861. {
  2862.    png_size_t avail;
  2863.  
  2864.    png_debug(1, "in png_write_filtered_row");
  2865.  
  2866.    png_debug1(2, "filter = %d", filtered_row[0]);
  2867.    /* Set up the zlib input buffer */
  2868.  
  2869.    png_ptr->zstream.next_in = filtered_row;
  2870.    png_ptr->zstream.avail_in = 0;
  2871.    avail = png_ptr->row_info.rowbytes + 1;
  2872.    /* Repeat until we have compressed all the data */
  2873.    do
  2874.    {
  2875.       int ret; /* Return of zlib */
  2876.  
  2877.       /* Record the number of bytes available - zlib supports at least 65535
  2878.        * bytes at one step, depending on the size of the zlib type 'uInt', the
  2879.        * maximum size zlib can write at once is ZLIB_IO_MAX (from pngpriv.h).
  2880.        * Use this because on 16 bit systems 'rowbytes' can be up to 65536 (i.e.
  2881.        * one more than 16 bits) and, in this case 'rowbytes+1' can overflow a
  2882.        * uInt.  ZLIB_IO_MAX can be safely reduced to cause zlib to be called
  2883.        * with smaller chunks of data.
  2884.        */
  2885.       if (png_ptr->zstream.avail_in == 0)
  2886.       {
  2887.          if (avail > ZLIB_IO_MAX)
  2888.          {
  2889.             png_ptr->zstream.avail_in  = ZLIB_IO_MAX;
  2890.             avail -= ZLIB_IO_MAX;
  2891.          }
  2892.  
  2893.          else
  2894.          {
  2895.             /* So this will fit in the available uInt space: */
  2896.             png_ptr->zstream.avail_in = (uInt)avail;
  2897.             avail = 0;
  2898.          }
  2899.       }
  2900.  
  2901.       /* Compress the data */
  2902.       ret = deflate(&png_ptr->zstream, Z_NO_FLUSH);
  2903.  
  2904.       /* Check for compression errors */
  2905.       if (ret != Z_OK)
  2906.       {
  2907.          if (png_ptr->zstream.msg != NULL)
  2908.             png_error(png_ptr, png_ptr->zstream.msg);
  2909.  
  2910.          else
  2911.             png_error(png_ptr, "zlib error");
  2912.       }
  2913.  
  2914.       /* See if it is time to write another IDAT */
  2915.       if (!(png_ptr->zstream.avail_out))
  2916.       {
  2917.          /* Write the IDAT and reset the zlib output buffer */
  2918.          png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
  2919.          png_ptr->zstream.next_out = png_ptr->zbuf;
  2920.          png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
  2921.       }
  2922.    /* Repeat until all data has been compressed */
  2923.    } while (avail > 0 || png_ptr->zstream.avail_in > 0);
  2924.  
  2925.    /* Swap the current and previous rows */
  2926.    if (png_ptr->prev_row != NULL)
  2927.    {
  2928.       png_bytep tptr;
  2929.  
  2930.       tptr = png_ptr->prev_row;
  2931.       png_ptr->prev_row = png_ptr->row_buf;
  2932.       png_ptr->row_buf = tptr;
  2933.    }
  2934.  
  2935.    /* Finish row - updates counters and flushes zlib if last row */
  2936.    png_write_finish_row(png_ptr);
  2937.  
  2938. #ifdef PNG_WRITE_FLUSH_SUPPORTED
  2939.    png_ptr->flush_rows++;
  2940.  
  2941.    if (png_ptr->flush_dist > 0 &&
  2942.        png_ptr->flush_rows >= png_ptr->flush_dist)
  2943.    {
  2944.       png_write_flush(png_ptr);
  2945.    }
  2946. #endif
  2947. }
  2948. #endif /* PNG_WRITE_SUPPORTED */
  2949.