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/*

 * jcparam.c

 *

 * Copyright (C) 1991-1998, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file contains optional default-setting code for the JPEG compressor.

 * Applications do not have to use this file, but those that don't use it

 * must know a lot more about the innards of the JPEG code.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

/*

 * Quantization table setup routines

 */

GLOBAL(void)

jpeg_add_quant_table (j_compress_ptr cinfo, int which_tbl,

		      const unsigned int *basic_table,

		      int scale_factor, boolean force_baseline)

/* Define a quantization table equal to the basic_table times

 * a scale factor (given as a percentage).

 * If force_baseline is TRUE, the computed quantization table entries

 * are limited to 1..255 for JPEG baseline compatibility.

 */

{

  JQUANT_TBL ** qtblptr;

  int i;

  long temp;

  /* Safety check to ensure start_compress not called yet. */

  if (cinfo->global_state != CSTATE_START)

    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  if (which_tbl < 0 || which_tbl >= NUM_QUANT_TBLS)

    ERREXIT1(cinfo, JERR_DQT_INDEX, which_tbl);

  qtblptr = & cinfo->quant_tbl_ptrs[which_tbl];

  if (*qtblptr == NULL)

    *qtblptr = jpeg_alloc_quant_table((j_common_ptr) cinfo);

  for (i = 0; i < DCTSIZE2; i++) {

    temp = ((long) basic_table[i] * scale_factor + 50L) / 100L;

    /* limit the values to the valid range */

    if (temp <= 0L) temp = 1L;

    if (temp > 32767L) temp = 32767L; /* max quantizer needed for 12 bits */

    if (force_baseline && temp > 255L)

      temp = 255L;		/* limit to baseline range if requested */

    (*qtblptr)->quantval[i] = (UINT16) temp;

  }

  /* Initialize sent_table FALSE so table will be written to JPEG file. */

  (*qtblptr)->sent_table = FALSE;

}

GLOBAL(void)

jpeg_set_linear_quality (j_compress_ptr cinfo, int scale_factor,

			 boolean force_baseline)

/* Set or change the 'quality' (quantization) setting, using default tables

 * and a straight percentage-scaling quality scale.  In most cases it's better

 * to use jpeg_set_quality (below); this entry point is provided for

 * applications that insist on a linear percentage scaling.

 */

{

  /* These are the sample quantization tables given in JPEG spec section K.1.

   * The spec says that the values given produce "good" quality, and

   * when divided by 2, "very good" quality.

   */

  static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = {

    16,  11,  10,  16,  24,  40,  51,  61,

    12,  12,  14,  19,  26,  58,  60,  55,

    14,  13,  16,  24,  40,  57,  69,  56,

    14,  17,  22,  29,  51,  87,  80,  62,

    18,  22,  37,  56,  68, 109, 103,  77,

    24,  35,  55,  64,  81, 104, 113,  92,

    49,  64,  78,  87, 103, 121, 120, 101,

    72,  92,  95,  98, 112, 100, 103,  99

  };

  static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = {

    17,  18,  24,  47,  99,  99,  99,  99,

    18,  21,  26,  66,  99,  99,  99,  99,

    24,  26,  56,  99,  99,  99,  99,  99,

    47,  66,  99,  99,  99,  99,  99,  99,

    99,  99,  99,  99,  99,  99,  99,  99,

    99,  99,  99,  99,  99,  99,  99,  99,

    99,  99,  99,  99,  99,  99,  99,  99,

    99,  99,  99,  99,  99,  99,  99,  99

  };

  /* Set up two quantization tables using the specified scaling */

  jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl,

		       scale_factor, force_baseline);

  jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl,

		       scale_factor, force_baseline);

}

GLOBAL(int)

jpeg_quality_scaling (int quality)

/* Convert a user-specified quality rating to a percentage scaling factor

 * for an underlying quantization table, using our recommended scaling curve.

 * The input 'quality' factor should be 0 (terrible) to 100 (very good).

 */

{

  /* Safety limit on quality factor.  Convert 0 to 1 to avoid zero divide. */

  if (quality <= 0) quality = 1;

  if (quality > 100) quality = 100;

  /* The basic table is used as-is (scaling 100) for a quality of 50.

   * Qualities 50..100 are converted to scaling percentage 200 - 2*Q;

   * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table

   * to make all the table entries 1 (hence, minimum quantization loss).

   * Qualities 1..50 are converted to scaling percentage 5000/Q.

   */

  if (quality < 50)

    quality = 5000 / quality;

  else

    quality = 200 - quality*2;

  return quality;

}

GLOBAL(void)

jpeg_set_quality (j_compress_ptr cinfo, int quality, boolean force_baseline)

/* Set or change the 'quality' (quantization) setting, using default tables.

 * This is the standard quality-adjusting entry point for typical user

 * interfaces; only those who want detailed control over quantization tables

 * would use the preceding three routines directly.

 */

{

  /* Convert user 0-100 rating to percentage scaling */

  quality = jpeg_quality_scaling(quality);

  /* Set up standard quality tables */

  jpeg_set_linear_quality(cinfo, quality, force_baseline);

}

/*

 * Huffman table setup routines

 */

LOCAL(void)

add_huff_table (j_compress_ptr cinfo,

		JHUFF_TBL **htblptr, const UINT8 *bits, const UINT8 *val)

/* Define a Huffman table */

{

  int nsymbols, len;

  if (*htblptr == NULL)

    *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);

  /* Copy the number-of-symbols-of-each-code-length counts */

  MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));

  /* Validate the counts.  We do this here mainly so we can copy the right

   * number of symbols from the val[] array, without risking marching off

   * the end of memory.  jchuff.c will do a more thorough test later.

   */

  nsymbols = 0;

  for (len = 1; len <= 16; len++)

    nsymbols += bits[len];

  if (nsymbols < 1 || nsymbols > 256)

    ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);

  MEMCOPY((*htblptr)->huffval, val, nsymbols * SIZEOF(UINT8));

  /* Initialize sent_table FALSE so table will be written to JPEG file. */

  (*htblptr)->sent_table = FALSE;

}

LOCAL(void)

std_huff_tables (j_compress_ptr cinfo)

/* Set up the standard Huffman tables (cf. JPEG standard section K.3) */

/* IMPORTANT: these are only valid for 8-bit data precision! */

{

  static const UINT8 bits_dc_luminance[17] =

    { /* 0-base */ 0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };

  static const UINT8 val_dc_luminance[] =

    { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };

  static const UINT8 bits_dc_chrominance[17] =

    { /* 0-base */ 0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };

  static const UINT8 val_dc_chrominance[] =

    { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };

  static const UINT8 bits_ac_luminance[17] =

    { /* 0-base */ 0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d };

  static const UINT8 val_ac_luminance[] =

    { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,

      0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,

      0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,

      0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,

      0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,

      0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,

      0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,

      0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,

      0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,

      0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,

      0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,

      0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,

      0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,

      0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,

      0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,

      0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,

      0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,

      0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,

      0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea,

      0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,

      0xf9, 0xfa };

  static const UINT8 bits_ac_chrominance[17] =

    { /* 0-base */ 0, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77 };

  static const UINT8 val_ac_chrominance[] =

    { 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,

      0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,

      0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,

      0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,

      0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,

      0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,

      0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,

      0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,

      0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,

      0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,

      0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,

      0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,

      0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,

      0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,

      0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,

      0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,

      0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,

      0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda,

      0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,

      0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,

      0xf9, 0xfa };

  add_huff_table(cinfo, &cinfo->dc_huff_tbl_ptrs[0],

		 bits_dc_luminance, val_dc_luminance);

  add_huff_table(cinfo, &cinfo->ac_huff_tbl_ptrs[0],

		 bits_ac_luminance, val_ac_luminance);

  add_huff_table(cinfo, &cinfo->dc_huff_tbl_ptrs[1],

		 bits_dc_chrominance, val_dc_chrominance);

  add_huff_table(cinfo, &cinfo->ac_huff_tbl_ptrs[1],

		 bits_ac_chrominance, val_ac_chrominance);

}

/*

 * Default parameter setup for compression.

 *

 * Applications that don't choose to use this routine must do their

 * own setup of all these parameters.  Alternately, you can call this

 * to establish defaults and then alter parameters selectively.  This

 * is the recommended approach since, if we add any new parameters,

 * your code will still work (they'll be set to reasonable defaults).

 */

GLOBAL(void)

jpeg_set_defaults (j_compress_ptr cinfo)

{

  int i;

  /* Safety check to ensure start_compress not called yet. */

  if (cinfo->global_state != CSTATE_START)

    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  /* Allocate comp_info array large enough for maximum component count.

   * Array is made permanent in case application wants to compress

   * multiple images at same param settings.

   */

  if (cinfo->comp_info == NULL)

    cinfo->comp_info = (jpeg_component_info *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,

				  MAX_COMPONENTS * SIZEOF(jpeg_component_info));

  /* Initialize everything not dependent on the color space */

  cinfo->data_precision = BITS_IN_JSAMPLE;

  /* Set up two quantization tables using default quality of 75 */

  jpeg_set_quality(cinfo, 75, TRUE);

  /* Set up two Huffman tables */

  std_huff_tables(cinfo);

  /* Initialize default arithmetic coding conditioning */

  for (i = 0; i < NUM_ARITH_TBLS; i++) {

    cinfo->arith_dc_L[i] = 0;

    cinfo->arith_dc_U[i] = 1;

    cinfo->arith_ac_K[i] = 5;

  }

  /* Default is no multiple-scan output */

  cinfo->scan_info = NULL;

  cinfo->num_scans = 0;

  /* Expect normal source image, not raw downsampled data */

  cinfo->raw_data_in = FALSE;

  /* Use Huffman coding, not arithmetic coding, by default */

  cinfo->arith_code = FALSE;

  /* By default, don't do extra passes to optimize entropy coding */

  cinfo->optimize_coding = FALSE;

  /* The standard Huffman tables are only valid for 8-bit data precision.

   * If the precision is higher, force optimization on so that usable

   * tables will be computed.  This test can be removed if default tables

   * are supplied that are valid for the desired precision.

   */

  if (cinfo->data_precision > 8)

    cinfo->optimize_coding = TRUE;

  /* By default, use the simpler non-cosited sampling alignment */

  cinfo->CCIR601_sampling = FALSE;

  /* No input smoothing */

  cinfo->smoothing_factor = 0;

  /* DCT algorithm preference */

  cinfo->dct_method = JDCT_DEFAULT;

  /* No restart markers */

  cinfo->restart_interval = 0;

  cinfo->restart_in_rows = 0;

  /* Fill in default JFIF marker parameters.  Note that whether the marker

   * will actually be written is determined by jpeg_set_colorspace.

   *

   * By default, the library emits JFIF version code 1.01.

   * An application that wants to emit JFIF 1.02 extension markers should set

   * JFIF_minor_version to 2.  We could probably get away with just defaulting

   * to 1.02, but there may still be some decoders in use that will complain

   * about that; saying 1.01 should minimize compatibility problems.

   */

  cinfo->JFIF_major_version = 1; /* Default JFIF version = 1.01 */

  cinfo->JFIF_minor_version = 1;

  cinfo->density_unit = 0;	/* Pixel size is unknown by default */

  cinfo->X_density = 1;		/* Pixel aspect ratio is square by default */

  cinfo->Y_density = 1;

  /* Choose JPEG colorspace based on input space, set defaults accordingly */

  jpeg_default_colorspace(cinfo);

}

/*

 * Select an appropriate JPEG colorspace for in_color_space.

 */

GLOBAL(void)

jpeg_default_colorspace (j_compress_ptr cinfo)

{

  switch (cinfo->in_color_space) {

  case JCS_GRAYSCALE:

    jpeg_set_colorspace(cinfo, JCS_GRAYSCALE);

    break;

  case JCS_RGB:

    jpeg_set_colorspace(cinfo, JCS_YCbCr);

    break;

  case JCS_YCbCr:

    jpeg_set_colorspace(cinfo, JCS_YCbCr);

    break;

  case JCS_CMYK:

    jpeg_set_colorspace(cinfo, JCS_CMYK); /* By default, no translation */

    break;

  case JCS_YCCK:

    jpeg_set_colorspace(cinfo, JCS_YCCK);

    break;

  case JCS_UNKNOWN:

    jpeg_set_colorspace(cinfo, JCS_UNKNOWN);

    break;

  default:

    ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

  }

}

/*

 * Set the JPEG colorspace, and choose colorspace-dependent default values.

 */

GLOBAL(void)

jpeg_set_colorspace (j_compress_ptr cinfo, J_COLOR_SPACE colorspace)

{

  jpeg_component_info * compptr;

  int ci;

#define SET_COMP(index,id,hsamp,vsamp,quant,dctbl,actbl)  \

  (compptr = &cinfo->comp_info[index], \

   compptr->component_id = (id), \

   compptr->h_samp_factor = (hsamp), \

   compptr->v_samp_factor = (vsamp), \

   compptr->quant_tbl_no = (quant), \

   compptr->dc_tbl_no = (dctbl), \

   compptr->ac_tbl_no = (actbl) )

  /* Safety check to ensure start_compress not called yet. */

  if (cinfo->global_state != CSTATE_START)

    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  /* For all colorspaces, we use Q and Huff tables 0 for luminance components,

   * tables 1 for chrominance components.

   */

  cinfo->jpeg_color_space = colorspace;

  cinfo->write_JFIF_header = FALSE; /* No marker for non-JFIF colorspaces */

  cinfo->write_Adobe_marker = FALSE; /* write no Adobe marker by default */

  switch (colorspace) {

  case JCS_GRAYSCALE:

    cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */

    cinfo->num_components = 1;

    /* JFIF specifies component ID 1 */

    SET_COMP(0, 1, 1,1, 0, 0,0);

    break;

  case JCS_RGB:

    cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag RGB */

    cinfo->num_components = 3;

    SET_COMP(0, 0x52 /* 'R' */, 1,1, 0, 0,0);

    SET_COMP(1, 0x47 /* 'G' */, 1,1, 0, 0,0);

    SET_COMP(2, 0x42 /* 'B' */, 1,1, 0, 0,0);

    break;

  case JCS_YCbCr:

    cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */

    cinfo->num_components = 3;

    /* JFIF specifies component IDs 1,2,3 */

    /* We default to 2x2 subsamples of chrominance */

    SET_COMP(0, 1, 2,2, 0, 0,0);

    SET_COMP(1, 2, 1,1, 1, 1,1);

    SET_COMP(2, 3, 1,1, 1, 1,1);

    break;

  case JCS_CMYK:

    cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag CMYK */

    cinfo->num_components = 4;

    SET_COMP(0, 0x43 /* 'C' */, 1,1, 0, 0,0);

    SET_COMP(1, 0x4D /* 'M' */, 1,1, 0, 0,0);

    SET_COMP(2, 0x59 /* 'Y' */, 1,1, 0, 0,0);

    SET_COMP(3, 0x4B /* 'K' */, 1,1, 0, 0,0);

    break;

  case JCS_YCCK:

    cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag YCCK */

    cinfo->num_components = 4;

    SET_COMP(0, 1, 2,2, 0, 0,0);

    SET_COMP(1, 2, 1,1, 1, 1,1);

    SET_COMP(2, 3, 1,1, 1, 1,1);

    SET_COMP(3, 4, 2,2, 0, 0,0);

    break;

  case JCS_UNKNOWN:

    cinfo->num_components = cinfo->input_components;

    if (cinfo->num_components < 1 || cinfo->num_components > MAX_COMPONENTS)

      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,

	       MAX_COMPONENTS);

    for (ci = 0; ci < cinfo->num_components; ci++) {

      SET_COMP(ci, ci, 1,1, 0, 0,0);

    }

    break;

  default:

    ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);

  }

}

#ifdef C_PROGRESSIVE_SUPPORTED

LOCAL(jpeg_scan_info *)

fill_a_scan (jpeg_scan_info * scanptr, int ci,

	     int Ss, int Se, int Ah, int Al)

/* Support routine: generate one scan for specified component */

{

  scanptr->comps_in_scan = 1;

  scanptr->component_index[0] = ci;

  scanptr->Ss = Ss;

  scanptr->Se = Se;

  scanptr->Ah = Ah;

  scanptr->Al = Al;

  scanptr++;

  return scanptr;

}

LOCAL(jpeg_scan_info *)

fill_scans (jpeg_scan_info * scanptr, int ncomps,

	    int Ss, int Se, int Ah, int Al)

/* Support routine: generate one scan for each component */

{

  int ci;

  for (ci = 0; ci < ncomps; ci++) {

    scanptr->comps_in_scan = 1;

    scanptr->component_index[0] = ci;

    scanptr->Ss = Ss;

    scanptr->Se = Se;

    scanptr->Ah = Ah;

    scanptr->Al = Al;

    scanptr++;

  }

  return scanptr;

}

LOCAL(jpeg_scan_info *)

fill_dc_scans (jpeg_scan_info * scanptr, int ncomps, int Ah, int Al)

/* Support routine: generate interleaved DC scan if possible, else N scans */

{

  int ci;

  if (ncomps <= MAX_COMPS_IN_SCAN) {

    /* Single interleaved DC scan */

    scanptr->comps_in_scan = ncomps;

    for (ci = 0; ci < ncomps; ci++)

      scanptr->component_index[ci] = ci;

    scanptr->Ss = scanptr->Se = 0;

    scanptr->Ah = Ah;

    scanptr->Al = Al;

    scanptr++;

  } else {

    /* Noninterleaved DC scan for each component */

    scanptr = fill_scans(scanptr, ncomps, 0, 0, Ah, Al);

  }

  return scanptr;

}

/*

 * Create a recommended progressive-JPEG script.

 * cinfo->num_components and cinfo->jpeg_color_space must be correct.

 */

GLOBAL(void)

jpeg_simple_progression (j_compress_ptr cinfo)

{

  int ncomps = cinfo->num_components;

  int nscans;

  jpeg_scan_info * scanptr;

  /* Safety check to ensure start_compress not called yet. */

  if (cinfo->global_state != CSTATE_START)

    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  /* Figure space needed for script.  Calculation must match code below! */

  if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {

    /* Custom script for YCbCr color images. */

    nscans = 10;

  } else {

    /* All-purpose script for other color spaces. */

    if (ncomps > MAX_COMPS_IN_SCAN)

      nscans = 6 * ncomps;	/* 2 DC + 4 AC scans per component */

    else

      nscans = 2 + 4 * ncomps;	/* 2 DC scans; 4 AC scans per component */

  }

  /* Allocate space for script.

   * We need to put it in the permanent pool in case the application performs

   * multiple compressions without changing the settings.  To avoid a memory

   * leak if jpeg_simple_progression is called repeatedly for the same JPEG

   * object, we try to re-use previously allocated space, and we allocate

   * enough space to handle YCbCr even if initially asked for grayscale.

   */

  if (cinfo->script_space == NULL || cinfo->script_space_size < nscans) {

    cinfo->script_space_size = MAX(nscans, 10);

    cinfo->script_space = (jpeg_scan_info *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,

			cinfo->script_space_size * SIZEOF(jpeg_scan_info));

  }

  scanptr = cinfo->script_space;

  cinfo->scan_info = scanptr;

  cinfo->num_scans = nscans;

  if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {

    /* Custom script for YCbCr color images. */

    /* Initial DC scan */

    scanptr = fill_dc_scans(scanptr, ncomps, 0, 1);

    /* Initial AC scan: get some luma data out in a hurry */

    scanptr = fill_a_scan(scanptr, 0, 1, 5, 0, 2);

    /* Chroma data is too small to be worth expending many scans on */

    scanptr = fill_a_scan(scanptr, 2, 1, 63, 0, 1);

    scanptr = fill_a_scan(scanptr, 1, 1, 63, 0, 1);

    /* Complete spectral selection for luma AC */

    scanptr = fill_a_scan(scanptr, 0, 6, 63, 0, 2);

    /* Refine next bit of luma AC */

    scanptr = fill_a_scan(scanptr, 0, 1, 63, 2, 1);

    /* Finish DC successive approximation */

    scanptr = fill_dc_scans(scanptr, ncomps, 1, 0);

    /* Finish AC successive approximation */

    scanptr = fill_a_scan(scanptr, 2, 1, 63, 1, 0);

    scanptr = fill_a_scan(scanptr, 1, 1, 63, 1, 0);

    /* Luma bottom bit comes last since it's usually largest scan */

    scanptr = fill_a_scan(scanptr, 0, 1, 63, 1, 0);

  } else {

    /* All-purpose script for other color spaces. */

    /* Successive approximation first pass */

    scanptr = fill_dc_scans(scanptr, ncomps, 0, 1);

    scanptr = fill_scans(scanptr, ncomps, 1, 5, 0, 2);

    scanptr = fill_scans(scanptr, ncomps, 6, 63, 0, 2);

    /* Successive approximation second pass */

    scanptr = fill_scans(scanptr, ncomps, 1, 63, 2, 1);

    /* Successive approximation final pass */

    scanptr = fill_dc_scans(scanptr, ncomps, 1, 0);

    scanptr = fill_scans(scanptr, ncomps, 1, 63, 1, 0);

  }

}

#endif /* C_PROGRESSIVE_SUPPORTED */