michael@0: /*
michael@0:  * jcparam.c
michael@0:  *
michael@0:  * This file was part of the Independent JPEG Group's software:
michael@0:  * Copyright (C) 1991-1998, Thomas G. Lane.
michael@0:  * Modified 2003-2008 by Guido Vollbeding.
michael@0:  * libjpeg-turbo Modifications:
michael@0:  * Copyright (C) 2009-2011, D. R. Commander.
michael@0:  * For conditions of distribution and use, see the accompanying README file.
michael@0:  *
michael@0:  * This file contains optional default-setting code for the JPEG compressor.
michael@0:  * Applications do not have to use this file, but those that don't use it
michael@0:  * must know a lot more about the innards of the JPEG code.
michael@0:  */
michael@0: 
michael@0: #define JPEG_INTERNALS
michael@0: #include "jinclude.h"
michael@0: #include "jpeglib.h"
michael@0: #include "jstdhuff.c"
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Quantization table setup routines
michael@0:  */
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_add_quant_table (j_compress_ptr cinfo, int which_tbl,
michael@0: 		      const unsigned int *basic_table,
michael@0: 		      int scale_factor, boolean force_baseline)
michael@0: /* Define a quantization table equal to the basic_table times
michael@0:  * a scale factor (given as a percentage).
michael@0:  * If force_baseline is TRUE, the computed quantization table entries
michael@0:  * are limited to 1..255 for JPEG baseline compatibility.
michael@0:  */
michael@0: {
michael@0:   JQUANT_TBL ** qtblptr;
michael@0:   int i;
michael@0:   long temp;
michael@0: 
michael@0:   /* Safety check to ensure start_compress not called yet. */
michael@0:   if (cinfo->global_state != CSTATE_START)
michael@0:     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
michael@0: 
michael@0:   if (which_tbl < 0 || which_tbl >= NUM_QUANT_TBLS)
michael@0:     ERREXIT1(cinfo, JERR_DQT_INDEX, which_tbl);
michael@0: 
michael@0:   qtblptr = & cinfo->quant_tbl_ptrs[which_tbl];
michael@0: 
michael@0:   if (*qtblptr == NULL)
michael@0:     *qtblptr = jpeg_alloc_quant_table((j_common_ptr) cinfo);
michael@0: 
michael@0:   for (i = 0; i < DCTSIZE2; i++) {
michael@0:     temp = ((long) basic_table[i] * scale_factor + 50L) / 100L;
michael@0:     /* limit the values to the valid range */
michael@0:     if (temp <= 0L) temp = 1L;
michael@0:     if (temp > 32767L) temp = 32767L; /* max quantizer needed for 12 bits */
michael@0:     if (force_baseline && temp > 255L)
michael@0:       temp = 255L;		/* limit to baseline range if requested */
michael@0:     (*qtblptr)->quantval[i] = (UINT16) temp;
michael@0:   }
michael@0: 
michael@0:   /* Initialize sent_table FALSE so table will be written to JPEG file. */
michael@0:   (*qtblptr)->sent_table = FALSE;
michael@0: }
michael@0: 
michael@0: 
michael@0: /* These are the sample quantization tables given in JPEG spec section K.1.
michael@0:  * The spec says that the values given produce "good" quality, and
michael@0:  * when divided by 2, "very good" quality.
michael@0:  */
michael@0: static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = {
michael@0:   16,  11,  10,  16,  24,  40,  51,  61,
michael@0:   12,  12,  14,  19,  26,  58,  60,  55,
michael@0:   14,  13,  16,  24,  40,  57,  69,  56,
michael@0:   14,  17,  22,  29,  51,  87,  80,  62,
michael@0:   18,  22,  37,  56,  68, 109, 103,  77,
michael@0:   24,  35,  55,  64,  81, 104, 113,  92,
michael@0:   49,  64,  78,  87, 103, 121, 120, 101,
michael@0:   72,  92,  95,  98, 112, 100, 103,  99
michael@0: };
michael@0: static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = {
michael@0:   17,  18,  24,  47,  99,  99,  99,  99,
michael@0:   18,  21,  26,  66,  99,  99,  99,  99,
michael@0:   24,  26,  56,  99,  99,  99,  99,  99,
michael@0:   47,  66,  99,  99,  99,  99,  99,  99,
michael@0:   99,  99,  99,  99,  99,  99,  99,  99,
michael@0:   99,  99,  99,  99,  99,  99,  99,  99,
michael@0:   99,  99,  99,  99,  99,  99,  99,  99,
michael@0:   99,  99,  99,  99,  99,  99,  99,  99
michael@0: };
michael@0: 
michael@0: 
michael@0: #if JPEG_LIB_VERSION >= 70
michael@0: GLOBAL(void)
michael@0: jpeg_default_qtables (j_compress_ptr cinfo, boolean force_baseline)
michael@0: /* Set or change the 'quality' (quantization) setting, using default tables
michael@0:  * and straight percentage-scaling quality scales.
michael@0:  * This entry point allows different scalings for luminance and chrominance.
michael@0:  */
michael@0: {
michael@0:   /* Set up two quantization tables using the specified scaling */
michael@0:   jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl,
michael@0: 		       cinfo->q_scale_factor[0], force_baseline);
michael@0:   jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl,
michael@0: 		       cinfo->q_scale_factor[1], force_baseline);
michael@0: }
michael@0: #endif
michael@0: 
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_set_linear_quality (j_compress_ptr cinfo, int scale_factor,
michael@0: 			 boolean force_baseline)
michael@0: /* Set or change the 'quality' (quantization) setting, using default tables
michael@0:  * and a straight percentage-scaling quality scale.  In most cases it's better
michael@0:  * to use jpeg_set_quality (below); this entry point is provided for
michael@0:  * applications that insist on a linear percentage scaling.
michael@0:  */
michael@0: {
michael@0:   /* Set up two quantization tables using the specified scaling */
michael@0:   jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl,
michael@0: 		       scale_factor, force_baseline);
michael@0:   jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl,
michael@0: 		       scale_factor, force_baseline);
michael@0: }
michael@0: 
michael@0: 
michael@0: GLOBAL(int)
michael@0: jpeg_quality_scaling (int quality)
michael@0: /* Convert a user-specified quality rating to a percentage scaling factor
michael@0:  * for an underlying quantization table, using our recommended scaling curve.
michael@0:  * The input 'quality' factor should be 0 (terrible) to 100 (very good).
michael@0:  */
michael@0: {
michael@0:   /* Safety limit on quality factor.  Convert 0 to 1 to avoid zero divide. */
michael@0:   if (quality <= 0) quality = 1;
michael@0:   if (quality > 100) quality = 100;
michael@0: 
michael@0:   /* The basic table is used as-is (scaling 100) for a quality of 50.
michael@0:    * Qualities 50..100 are converted to scaling percentage 200 - 2*Q;
michael@0:    * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table
michael@0:    * to make all the table entries 1 (hence, minimum quantization loss).
michael@0:    * Qualities 1..50 are converted to scaling percentage 5000/Q.
michael@0:    */
michael@0:   if (quality < 50)
michael@0:     quality = 5000 / quality;
michael@0:   else
michael@0:     quality = 200 - quality*2;
michael@0: 
michael@0:   return quality;
michael@0: }
michael@0: 
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_set_quality (j_compress_ptr cinfo, int quality, boolean force_baseline)
michael@0: /* Set or change the 'quality' (quantization) setting, using default tables.
michael@0:  * This is the standard quality-adjusting entry point for typical user
michael@0:  * interfaces; only those who want detailed control over quantization tables
michael@0:  * would use the preceding three routines directly.
michael@0:  */
michael@0: {
michael@0:   /* Convert user 0-100 rating to percentage scaling */
michael@0:   quality = jpeg_quality_scaling(quality);
michael@0: 
michael@0:   /* Set up standard quality tables */
michael@0:   jpeg_set_linear_quality(cinfo, quality, force_baseline);
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Default parameter setup for compression.
michael@0:  *
michael@0:  * Applications that don't choose to use this routine must do their
michael@0:  * own setup of all these parameters.  Alternately, you can call this
michael@0:  * to establish defaults and then alter parameters selectively.  This
michael@0:  * is the recommended approach since, if we add any new parameters,
michael@0:  * your code will still work (they'll be set to reasonable defaults).
michael@0:  */
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_set_defaults (j_compress_ptr cinfo)
michael@0: {
michael@0:   int i;
michael@0: 
michael@0:   /* Safety check to ensure start_compress not called yet. */
michael@0:   if (cinfo->global_state != CSTATE_START)
michael@0:     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
michael@0: 
michael@0:   /* Allocate comp_info array large enough for maximum component count.
michael@0:    * Array is made permanent in case application wants to compress
michael@0:    * multiple images at same param settings.
michael@0:    */
michael@0:   if (cinfo->comp_info == NULL)
michael@0:     cinfo->comp_info = (jpeg_component_info *)
michael@0:       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
michael@0: 				  MAX_COMPONENTS * SIZEOF(jpeg_component_info));
michael@0: 
michael@0:   /* Initialize everything not dependent on the color space */
michael@0: 
michael@0: #if JPEG_LIB_VERSION >= 70
michael@0:   cinfo->scale_num = 1;		/* 1:1 scaling */
michael@0:   cinfo->scale_denom = 1;
michael@0: #endif
michael@0:   cinfo->data_precision = BITS_IN_JSAMPLE;
michael@0:   /* Set up two quantization tables using default quality of 75 */
michael@0:   jpeg_set_quality(cinfo, 75, TRUE);
michael@0:   /* Set up two Huffman tables */
michael@0:   std_huff_tables((j_common_ptr) cinfo);
michael@0: 
michael@0:   /* Initialize default arithmetic coding conditioning */
michael@0:   for (i = 0; i < NUM_ARITH_TBLS; i++) {
michael@0:     cinfo->arith_dc_L[i] = 0;
michael@0:     cinfo->arith_dc_U[i] = 1;
michael@0:     cinfo->arith_ac_K[i] = 5;
michael@0:   }
michael@0: 
michael@0:   /* Default is no multiple-scan output */
michael@0:   cinfo->scan_info = NULL;
michael@0:   cinfo->num_scans = 0;
michael@0: 
michael@0:   /* Expect normal source image, not raw downsampled data */
michael@0:   cinfo->raw_data_in = FALSE;
michael@0: 
michael@0:   /* Use Huffman coding, not arithmetic coding, by default */
michael@0:   cinfo->arith_code = FALSE;
michael@0: 
michael@0:   /* By default, don't do extra passes to optimize entropy coding */
michael@0:   cinfo->optimize_coding = FALSE;
michael@0:   /* The standard Huffman tables are only valid for 8-bit data precision.
michael@0:    * If the precision is higher, force optimization on so that usable
michael@0:    * tables will be computed.  This test can be removed if default tables
michael@0:    * are supplied that are valid for the desired precision.
michael@0:    */
michael@0:   if (cinfo->data_precision > 8)
michael@0:     cinfo->optimize_coding = TRUE;
michael@0: 
michael@0:   /* By default, use the simpler non-cosited sampling alignment */
michael@0:   cinfo->CCIR601_sampling = FALSE;
michael@0: 
michael@0: #if JPEG_LIB_VERSION >= 70
michael@0:   /* By default, apply fancy downsampling */
michael@0:   cinfo->do_fancy_downsampling = TRUE;
michael@0: #endif
michael@0: 
michael@0:   /* No input smoothing */
michael@0:   cinfo->smoothing_factor = 0;
michael@0: 
michael@0:   /* DCT algorithm preference */
michael@0:   cinfo->dct_method = JDCT_DEFAULT;
michael@0: 
michael@0:   /* No restart markers */
michael@0:   cinfo->restart_interval = 0;
michael@0:   cinfo->restart_in_rows = 0;
michael@0: 
michael@0:   /* Fill in default JFIF marker parameters.  Note that whether the marker
michael@0:    * will actually be written is determined by jpeg_set_colorspace.
michael@0:    *
michael@0:    * By default, the library emits JFIF version code 1.01.
michael@0:    * An application that wants to emit JFIF 1.02 extension markers should set
michael@0:    * JFIF_minor_version to 2.  We could probably get away with just defaulting
michael@0:    * to 1.02, but there may still be some decoders in use that will complain
michael@0:    * about that; saying 1.01 should minimize compatibility problems.
michael@0:    */
michael@0:   cinfo->JFIF_major_version = 1; /* Default JFIF version = 1.01 */
michael@0:   cinfo->JFIF_minor_version = 1;
michael@0:   cinfo->density_unit = 0;	/* Pixel size is unknown by default */
michael@0:   cinfo->X_density = 1;		/* Pixel aspect ratio is square by default */
michael@0:   cinfo->Y_density = 1;
michael@0: 
michael@0:   /* Choose JPEG colorspace based on input space, set defaults accordingly */
michael@0: 
michael@0:   jpeg_default_colorspace(cinfo);
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Select an appropriate JPEG colorspace for in_color_space.
michael@0:  */
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_default_colorspace (j_compress_ptr cinfo)
michael@0: {
michael@0:   switch (cinfo->in_color_space) {
michael@0:   case JCS_GRAYSCALE:
michael@0:     jpeg_set_colorspace(cinfo, JCS_GRAYSCALE);
michael@0:     break;
michael@0:   case JCS_RGB:
michael@0:   case JCS_EXT_RGB:
michael@0:   case JCS_EXT_RGBX:
michael@0:   case JCS_EXT_BGR:
michael@0:   case JCS_EXT_BGRX:
michael@0:   case JCS_EXT_XBGR:
michael@0:   case JCS_EXT_XRGB:
michael@0:   case JCS_EXT_RGBA:
michael@0:   case JCS_EXT_BGRA:
michael@0:   case JCS_EXT_ABGR:
michael@0:   case JCS_EXT_ARGB:
michael@0:     jpeg_set_colorspace(cinfo, JCS_YCbCr);
michael@0:     break;
michael@0:   case JCS_YCbCr:
michael@0:     jpeg_set_colorspace(cinfo, JCS_YCbCr);
michael@0:     break;
michael@0:   case JCS_CMYK:
michael@0:     jpeg_set_colorspace(cinfo, JCS_CMYK); /* By default, no translation */
michael@0:     break;
michael@0:   case JCS_YCCK:
michael@0:     jpeg_set_colorspace(cinfo, JCS_YCCK);
michael@0:     break;
michael@0:   case JCS_UNKNOWN:
michael@0:     jpeg_set_colorspace(cinfo, JCS_UNKNOWN);
michael@0:     break;
michael@0:   default:
michael@0:     ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Set the JPEG colorspace, and choose colorspace-dependent default values.
michael@0:  */
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_set_colorspace (j_compress_ptr cinfo, J_COLOR_SPACE colorspace)
michael@0: {
michael@0:   jpeg_component_info * compptr;
michael@0:   int ci;
michael@0: 
michael@0: #define SET_COMP(index,id,hsamp,vsamp,quant,dctbl,actbl)  \
michael@0:   (compptr = &cinfo->comp_info[index], \
michael@0:    compptr->component_id = (id), \
michael@0:    compptr->h_samp_factor = (hsamp), \
michael@0:    compptr->v_samp_factor = (vsamp), \
michael@0:    compptr->quant_tbl_no = (quant), \
michael@0:    compptr->dc_tbl_no = (dctbl), \
michael@0:    compptr->ac_tbl_no = (actbl) )
michael@0: 
michael@0:   /* Safety check to ensure start_compress not called yet. */
michael@0:   if (cinfo->global_state != CSTATE_START)
michael@0:     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
michael@0: 
michael@0:   /* For all colorspaces, we use Q and Huff tables 0 for luminance components,
michael@0:    * tables 1 for chrominance components.
michael@0:    */
michael@0: 
michael@0:   cinfo->jpeg_color_space = colorspace;
michael@0: 
michael@0:   cinfo->write_JFIF_header = FALSE; /* No marker for non-JFIF colorspaces */
michael@0:   cinfo->write_Adobe_marker = FALSE; /* write no Adobe marker by default */
michael@0: 
michael@0:   switch (colorspace) {
michael@0:   case JCS_GRAYSCALE:
michael@0:     cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */
michael@0:     cinfo->num_components = 1;
michael@0:     /* JFIF specifies component ID 1 */
michael@0:     SET_COMP(0, 1, 1,1, 0, 0,0);
michael@0:     break;
michael@0:   case JCS_RGB:
michael@0:     cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag RGB */
michael@0:     cinfo->num_components = 3;
michael@0:     SET_COMP(0, 0x52 /* 'R' */, 1,1, 0, 0,0);
michael@0:     SET_COMP(1, 0x47 /* 'G' */, 1,1, 0, 0,0);
michael@0:     SET_COMP(2, 0x42 /* 'B' */, 1,1, 0, 0,0);
michael@0:     break;
michael@0:   case JCS_YCbCr:
michael@0:     cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */
michael@0:     cinfo->num_components = 3;
michael@0:     /* JFIF specifies component IDs 1,2,3 */
michael@0:     /* We default to 2x2 subsamples of chrominance */
michael@0:     SET_COMP(0, 1, 2,2, 0, 0,0);
michael@0:     SET_COMP(1, 2, 1,1, 1, 1,1);
michael@0:     SET_COMP(2, 3, 1,1, 1, 1,1);
michael@0:     break;
michael@0:   case JCS_CMYK:
michael@0:     cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag CMYK */
michael@0:     cinfo->num_components = 4;
michael@0:     SET_COMP(0, 0x43 /* 'C' */, 1,1, 0, 0,0);
michael@0:     SET_COMP(1, 0x4D /* 'M' */, 1,1, 0, 0,0);
michael@0:     SET_COMP(2, 0x59 /* 'Y' */, 1,1, 0, 0,0);
michael@0:     SET_COMP(3, 0x4B /* 'K' */, 1,1, 0, 0,0);
michael@0:     break;
michael@0:   case JCS_YCCK:
michael@0:     cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag YCCK */
michael@0:     cinfo->num_components = 4;
michael@0:     SET_COMP(0, 1, 2,2, 0, 0,0);
michael@0:     SET_COMP(1, 2, 1,1, 1, 1,1);
michael@0:     SET_COMP(2, 3, 1,1, 1, 1,1);
michael@0:     SET_COMP(3, 4, 2,2, 0, 0,0);
michael@0:     break;
michael@0:   case JCS_UNKNOWN:
michael@0:     cinfo->num_components = cinfo->input_components;
michael@0:     if (cinfo->num_components < 1 || cinfo->num_components > MAX_COMPONENTS)
michael@0:       ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
michael@0: 	       MAX_COMPONENTS);
michael@0:     for (ci = 0; ci < cinfo->num_components; ci++) {
michael@0:       SET_COMP(ci, ci, 1,1, 0, 0,0);
michael@0:     }
michael@0:     break;
michael@0:   default:
michael@0:     ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: #ifdef C_PROGRESSIVE_SUPPORTED
michael@0: 
michael@0: LOCAL(jpeg_scan_info *)
michael@0: fill_a_scan (jpeg_scan_info * scanptr, int ci,
michael@0: 	     int Ss, int Se, int Ah, int Al)
michael@0: /* Support routine: generate one scan for specified component */
michael@0: {
michael@0:   scanptr->comps_in_scan = 1;
michael@0:   scanptr->component_index[0] = ci;
michael@0:   scanptr->Ss = Ss;
michael@0:   scanptr->Se = Se;
michael@0:   scanptr->Ah = Ah;
michael@0:   scanptr->Al = Al;
michael@0:   scanptr++;
michael@0:   return scanptr;
michael@0: }
michael@0: 
michael@0: LOCAL(jpeg_scan_info *)
michael@0: fill_scans (jpeg_scan_info * scanptr, int ncomps,
michael@0: 	    int Ss, int Se, int Ah, int Al)
michael@0: /* Support routine: generate one scan for each component */
michael@0: {
michael@0:   int ci;
michael@0: 
michael@0:   for (ci = 0; ci < ncomps; ci++) {
michael@0:     scanptr->comps_in_scan = 1;
michael@0:     scanptr->component_index[0] = ci;
michael@0:     scanptr->Ss = Ss;
michael@0:     scanptr->Se = Se;
michael@0:     scanptr->Ah = Ah;
michael@0:     scanptr->Al = Al;
michael@0:     scanptr++;
michael@0:   }
michael@0:   return scanptr;
michael@0: }
michael@0: 
michael@0: LOCAL(jpeg_scan_info *)
michael@0: fill_dc_scans (jpeg_scan_info * scanptr, int ncomps, int Ah, int Al)
michael@0: /* Support routine: generate interleaved DC scan if possible, else N scans */
michael@0: {
michael@0:   int ci;
michael@0: 
michael@0:   if (ncomps <= MAX_COMPS_IN_SCAN) {
michael@0:     /* Single interleaved DC scan */
michael@0:     scanptr->comps_in_scan = ncomps;
michael@0:     for (ci = 0; ci < ncomps; ci++)
michael@0:       scanptr->component_index[ci] = ci;
michael@0:     scanptr->Ss = scanptr->Se = 0;
michael@0:     scanptr->Ah = Ah;
michael@0:     scanptr->Al = Al;
michael@0:     scanptr++;
michael@0:   } else {
michael@0:     /* Noninterleaved DC scan for each component */
michael@0:     scanptr = fill_scans(scanptr, ncomps, 0, 0, Ah, Al);
michael@0:   }
michael@0:   return scanptr;
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Create a recommended progressive-JPEG script.
michael@0:  * cinfo->num_components and cinfo->jpeg_color_space must be correct.
michael@0:  */
michael@0: 
michael@0: GLOBAL(void)
michael@0: jpeg_simple_progression (j_compress_ptr cinfo)
michael@0: {
michael@0:   int ncomps = cinfo->num_components;
michael@0:   int nscans;
michael@0:   jpeg_scan_info * scanptr;
michael@0: 
michael@0:   /* Safety check to ensure start_compress not called yet. */
michael@0:   if (cinfo->global_state != CSTATE_START)
michael@0:     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
michael@0: 
michael@0:   /* Figure space needed for script.  Calculation must match code below! */
michael@0:   if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {
michael@0:     /* Custom script for YCbCr color images. */
michael@0:     nscans = 10;
michael@0:   } else {
michael@0:     /* All-purpose script for other color spaces. */
michael@0:     if (ncomps > MAX_COMPS_IN_SCAN)
michael@0:       nscans = 6 * ncomps;	/* 2 DC + 4 AC scans per component */
michael@0:     else
michael@0:       nscans = 2 + 4 * ncomps;	/* 2 DC scans; 4 AC scans per component */
michael@0:   }
michael@0: 
michael@0:   /* Allocate space for script.
michael@0:    * We need to put it in the permanent pool in case the application performs
michael@0:    * multiple compressions without changing the settings.  To avoid a memory
michael@0:    * leak if jpeg_simple_progression is called repeatedly for the same JPEG
michael@0:    * object, we try to re-use previously allocated space, and we allocate
michael@0:    * enough space to handle YCbCr even if initially asked for grayscale.
michael@0:    */
michael@0:   if (cinfo->script_space == NULL || cinfo->script_space_size < nscans) {
michael@0:     cinfo->script_space_size = MAX(nscans, 10);
michael@0:     cinfo->script_space = (jpeg_scan_info *)
michael@0:       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
michael@0: 			cinfo->script_space_size * SIZEOF(jpeg_scan_info));
michael@0:   }
michael@0:   scanptr = cinfo->script_space;
michael@0:   cinfo->scan_info = scanptr;
michael@0:   cinfo->num_scans = nscans;
michael@0: 
michael@0:   if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) {
michael@0:     /* Custom script for YCbCr color images. */
michael@0:     /* Initial DC scan */
michael@0:     scanptr = fill_dc_scans(scanptr, ncomps, 0, 1);
michael@0:     /* Initial AC scan: get some luma data out in a hurry */
michael@0:     scanptr = fill_a_scan(scanptr, 0, 1, 5, 0, 2);
michael@0:     /* Chroma data is too small to be worth expending many scans on */
michael@0:     scanptr = fill_a_scan(scanptr, 2, 1, 63, 0, 1);
michael@0:     scanptr = fill_a_scan(scanptr, 1, 1, 63, 0, 1);
michael@0:     /* Complete spectral selection for luma AC */
michael@0:     scanptr = fill_a_scan(scanptr, 0, 6, 63, 0, 2);
michael@0:     /* Refine next bit of luma AC */
michael@0:     scanptr = fill_a_scan(scanptr, 0, 1, 63, 2, 1);
michael@0:     /* Finish DC successive approximation */
michael@0:     scanptr = fill_dc_scans(scanptr, ncomps, 1, 0);
michael@0:     /* Finish AC successive approximation */
michael@0:     scanptr = fill_a_scan(scanptr, 2, 1, 63, 1, 0);
michael@0:     scanptr = fill_a_scan(scanptr, 1, 1, 63, 1, 0);
michael@0:     /* Luma bottom bit comes last since it's usually largest scan */
michael@0:     scanptr = fill_a_scan(scanptr, 0, 1, 63, 1, 0);
michael@0:   } else {
michael@0:     /* All-purpose script for other color spaces. */
michael@0:     /* Successive approximation first pass */
michael@0:     scanptr = fill_dc_scans(scanptr, ncomps, 0, 1);
michael@0:     scanptr = fill_scans(scanptr, ncomps, 1, 5, 0, 2);
michael@0:     scanptr = fill_scans(scanptr, ncomps, 6, 63, 0, 2);
michael@0:     /* Successive approximation second pass */
michael@0:     scanptr = fill_scans(scanptr, ncomps, 1, 63, 2, 1);
michael@0:     /* Successive approximation final pass */
michael@0:     scanptr = fill_dc_scans(scanptr, ncomps, 1, 0);
michael@0:     scanptr = fill_scans(scanptr, ncomps, 1, 63, 1, 0);
michael@0:   }
michael@0: }
michael@0: 
michael@0: #endif /* C_PROGRESSIVE_SUPPORTED */