www.pudn.com > imgport.rar > jcparam.c, change:2008-11-05,size:21885b


/* 
 * 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 */