www.pudn.com > imgport.rar > jdmaster.c, change:2008-11-05,size:20266b


/* 
 * jdmaster.c 
 * 
 * Copyright (C) 1991-1997, 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 master control logic for the JPEG decompressor. 
 * These routines are concerned with selecting the modules to be executed 
 * and with determining the number of passes and the work to be done in each 
 * pass. 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
/* Private state */ 
 
typedef struct { 
  struct jpeg_decomp_master pub; /* public fields */ 
 
  int pass_number;		/* # of passes completed */ 
 
  boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */ 
 
  /* Saved references to initialized quantizer modules, 
   * in case we need to switch modes. 
   */ 
  struct jpeg_color_quantizer * quantizer_1pass; 
  struct jpeg_color_quantizer * quantizer_2pass; 
} my_decomp_master; 
 
typedef my_decomp_master * my_master_ptr; 
 
 
/* 
 * Determine whether merged upsample/color conversion should be used. 
 * CRUCIAL: this must match the actual capabilities of jdmerge.c! 
 */ 
 
LOCAL(boolean) 
use_merged_upsample (j_decompress_ptr cinfo) 
{ 
#ifdef UPSAMPLE_MERGING_SUPPORTED 
  /* Merging is the equivalent of plain box-filter upsampling */ 
  if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling) 
    return FALSE; 
  /* jdmerge.c only supports YCC=>RGB color conversion */ 
  if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 || 
      cinfo->out_color_space != JCS_RGB || 
      cinfo->out_color_components != RGB_PIXELSIZE) 
    return FALSE; 
  /* and it only handles 2h1v or 2h2v sampling ratios */ 
  if (cinfo->comp_info[0].h_samp_factor != 2 || 
      cinfo->comp_info[1].h_samp_factor != 1 || 
      cinfo->comp_info[2].h_samp_factor != 1 || 
      cinfo->comp_info[0].v_samp_factor >  2 || 
      cinfo->comp_info[1].v_samp_factor != 1 || 
      cinfo->comp_info[2].v_samp_factor != 1) 
    return FALSE; 
  /* furthermore, it doesn't work if we've scaled the IDCTs differently */ 
  if (cinfo->comp_info[0].DCT_scaled_size != cinfo->min_DCT_scaled_size || 
      cinfo->comp_info[1].DCT_scaled_size != cinfo->min_DCT_scaled_size || 
      cinfo->comp_info[2].DCT_scaled_size != cinfo->min_DCT_scaled_size) 
    return FALSE; 
  /* ??? also need to test for upsample-time rescaling, when & if supported */ 
  return TRUE;			/* by golly, it'll work... */ 
#else 
  return FALSE; 
#endif 
} 
 
 
/* 
 * Compute output image dimensions and related values. 
 * NOTE: this is exported for possible use by application. 
 * Hence it mustn't do anything that can't be done twice. 
 * Also note that it may be called before the master module is initialized! 
 */ 
 
GLOBAL(void) 
jpeg_calc_output_dimensions (j_decompress_ptr cinfo) 
/* Do computations that are needed before master selection phase */ 
{ 
#ifdef IDCT_SCALING_SUPPORTED 
  int ci; 
  jpeg_component_info *compptr; 
#endif 
 
  /* Prevent application from calling me at wrong times */ 
  if (cinfo->global_state != DSTATE_READY) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
 
#ifdef IDCT_SCALING_SUPPORTED 
 
  /* Compute actual output image dimensions and DCT scaling choices. */ 
  if (cinfo->scale_num * 8 <= cinfo->scale_denom) { 
    /* Provide 1/8 scaling */ 
    cinfo->output_width = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width, 8L); 
    cinfo->output_height = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height, 8L); 
    cinfo->min_DCT_scaled_size = 1; 
  } else if (cinfo->scale_num * 4 <= cinfo->scale_denom) { 
    /* Provide 1/4 scaling */ 
    cinfo->output_width = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width, 4L); 
    cinfo->output_height = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height, 4L); 
    cinfo->min_DCT_scaled_size = 2; 
  } else if (cinfo->scale_num * 2 <= cinfo->scale_denom) { 
    /* Provide 1/2 scaling */ 
    cinfo->output_width = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width, 2L); 
    cinfo->output_height = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height, 2L); 
    cinfo->min_DCT_scaled_size = 4; 
  } else { 
    /* Provide 1/1 scaling */ 
    cinfo->output_width = cinfo->image_width; 
    cinfo->output_height = cinfo->image_height; 
    cinfo->min_DCT_scaled_size = DCTSIZE; 
  } 
  /* In selecting the actual DCT scaling for each component, we try to 
   * scale up the chroma components via IDCT scaling rather than upsampling. 
   * This saves time if the upsampler gets to use 1:1 scaling. 
   * Note this code assumes that the supported DCT scalings are powers of 2. 
   */ 
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
       ci++, compptr++) { 
    int ssize = cinfo->min_DCT_scaled_size; 
    while (ssize < DCTSIZE && 
	   (compptr->h_samp_factor * ssize * 2 <= 
	    cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) && 
	   (compptr->v_samp_factor * ssize * 2 <= 
	    cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size)) { 
      ssize = ssize * 2; 
    } 
    compptr->DCT_scaled_size = ssize; 
  } 
 
  /* Recompute downsampled dimensions of components; 
   * application needs to know these if using raw downsampled data. 
   */ 
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
       ci++, compptr++) { 
    /* Size in samples, after IDCT scaling */ 
    compptr->downsampled_width = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width * 
		    (long) (compptr->h_samp_factor * compptr->DCT_scaled_size), 
		    (long) (cinfo->max_h_samp_factor * DCTSIZE)); 
    compptr->downsampled_height = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height * 
		    (long) (compptr->v_samp_factor * compptr->DCT_scaled_size), 
		    (long) (cinfo->max_v_samp_factor * DCTSIZE)); 
  } 
 
#else /* !IDCT_SCALING_SUPPORTED */ 
 
  /* Hardwire it to "no scaling" */ 
  cinfo->output_width = cinfo->image_width; 
  cinfo->output_height = cinfo->image_height; 
  /* jdinput.c has already initialized DCT_scaled_size to DCTSIZE, 
   * and has computed unscaled downsampled_width and downsampled_height. 
   */ 
 
#endif /* IDCT_SCALING_SUPPORTED */ 
 
  /* Report number of components in selected colorspace. */ 
  /* Probably this should be in the color conversion module... */ 
  switch (cinfo->out_color_space) { 
  case JCS_GRAYSCALE: 
    cinfo->out_color_components = 1; 
    break; 
  case JCS_RGB: 
#if RGB_PIXELSIZE != 3 
    cinfo->out_color_components = RGB_PIXELSIZE; 
    break; 
#endif /* else share code with YCbCr */ 
  case JCS_YCbCr: 
    cinfo->out_color_components = 3; 
    break; 
  case JCS_CMYK: 
  case JCS_YCCK: 
    cinfo->out_color_components = 4; 
    break; 
  default:			/* else must be same colorspace as in file */ 
    cinfo->out_color_components = cinfo->num_components; 
    break; 
  } 
  cinfo->output_components = (cinfo->quantize_colors ? 1 : 
			      cinfo->out_color_components); 
 
  /* See if upsampler will want to emit more than one row at a time */ 
  if (use_merged_upsample(cinfo)) 
    cinfo->rec_outbuf_height = cinfo->max_v_samp_factor; 
  else 
    cinfo->rec_outbuf_height = 1; 
} 
 
 
/* 
 * Several decompression processes need to range-limit values to the range 
 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range 
 * due to noise introduced by quantization, roundoff error, etc.  These 
 * processes are inner loops and need to be as fast as possible.  On most 
 * machines, particularly CPUs with pipelines or instruction prefetch, 
 * a (subscript-check-less) C table lookup 
 *		x = sample_range_limit[x]; 
 * is faster than explicit tests 
 *		if (x < 0)  x = 0; 
 *		else if (x > MAXJSAMPLE)  x = MAXJSAMPLE; 
 * These processes all use a common table prepared by the routine below. 
 * 
 * For most steps we can mathematically guarantee that the initial value 
 * of x is within MAXJSAMPLE+1 of the legal range, so a table running from 
 * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient.  But for the initial 
 * limiting step (just after the IDCT), a wildly out-of-range value is 
 * possible if the input data is corrupt.  To avoid any chance of indexing 
 * off the end of memory and getting a bad-pointer trap, we perform the 
 * post-IDCT limiting thus: 
 *		x = range_limit[x & MASK]; 
 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit 
 * samples.  Under normal circumstances this is more than enough range and 
 * a correct output will be generated; with bogus input data the mask will 
 * cause wraparound, and we will safely generate a bogus-but-in-range output. 
 * For the post-IDCT step, we want to convert the data from signed to unsigned 
 * representation by adding CENTERJSAMPLE at the same time that we limit it. 
 * So the post-IDCT limiting table ends up looking like this: 
 *   CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE, 
 *   MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), 
 *   0          (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times), 
 *   0,1,...,CENTERJSAMPLE-1 
 * Negative inputs select values from the upper half of the table after 
 * masking. 
 * 
 * We can save some space by overlapping the start of the post-IDCT table 
 * with the simpler range limiting table.  The post-IDCT table begins at 
 * sample_range_limit + CENTERJSAMPLE. 
 * 
 * Note that the table is allocated in near data space on PCs; it's small 
 * enough and used often enough to justify this. 
 */ 
 
LOCAL(void) 
prepare_range_limit_table (j_decompress_ptr cinfo) 
/* Allocate and fill in the sample_range_limit table */ 
{ 
  JSAMPLE * table; 
  int i; 
 
  table = (JSAMPLE *) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
		(5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE)); 
  table += (MAXJSAMPLE+1);	/* allow negative subscripts of simple table */ 
  cinfo->sample_range_limit = table; 
  /* First segment of "simple" table: limit[x] = 0 for x < 0 */ 
  MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE)); 
  /* Main part of "simple" table: limit[x] = x */ 
  for (i = 0; i <= MAXJSAMPLE; i++) 
    table[i] = (JSAMPLE) i; 
  table += CENTERJSAMPLE;	/* Point to where post-IDCT table starts */ 
  /* End of simple table, rest of first half of post-IDCT table */ 
  for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++) 
    table[i] = MAXJSAMPLE; 
  /* Second half of post-IDCT table */ 
  MEMZERO(table + (2 * (MAXJSAMPLE+1)), 
	  (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE)); 
  MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE), 
	  cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE)); 
} 
 
 
/* 
 * Master selection of decompression modules. 
 * This is done once at jpeg_start_decompress time.  We determine 
 * which modules will be used and give them appropriate initialization calls. 
 * We also initialize the decompressor input side to begin consuming data. 
 * 
 * Since jpeg_read_header has finished, we know what is in the SOF 
 * and (first) SOS markers.  We also have all the application parameter 
 * settings. 
 */ 
 
LOCAL(void) 
master_selection (j_decompress_ptr cinfo) 
{ 
  my_master_ptr master = (my_master_ptr) cinfo->master; 
  boolean use_c_buffer; 
  long samplesperrow; 
  JDIMENSION jd_samplesperrow; 
 
  /* Initialize dimensions and other stuff */ 
  jpeg_calc_output_dimensions(cinfo); 
  prepare_range_limit_table(cinfo); 
 
  /* Width of an output scanline must be representable as JDIMENSION. */ 
  samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components; 
  jd_samplesperrow = (JDIMENSION) samplesperrow; 
  if ((long) jd_samplesperrow != samplesperrow) 
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW); 
 
  /* Initialize my private state */ 
  master->pass_number = 0; 
  master->using_merged_upsample = use_merged_upsample(cinfo); 
 
  /* Color quantizer selection */ 
  master->quantizer_1pass = NULL; 
  master->quantizer_2pass = NULL; 
  /* No mode changes if not using buffered-image mode. */ 
  if (! cinfo->quantize_colors || ! cinfo->buffered_image) { 
    cinfo->enable_1pass_quant = FALSE; 
    cinfo->enable_external_quant = FALSE; 
    cinfo->enable_2pass_quant = FALSE; 
  } 
  if (cinfo->quantize_colors) { 
    if (cinfo->raw_data_out) 
      ERREXIT(cinfo, JERR_NOTIMPL); 
    /* 2-pass quantizer only works in 3-component color space. */ 
    if (cinfo->out_color_components != 3) { 
      cinfo->enable_1pass_quant = TRUE; 
      cinfo->enable_external_quant = FALSE; 
      cinfo->enable_2pass_quant = FALSE; 
      cinfo->colormap = NULL; 
    } else if (cinfo->colormap != NULL) { 
      cinfo->enable_external_quant = TRUE; 
    } else if (cinfo->two_pass_quantize) { 
      cinfo->enable_2pass_quant = TRUE; 
    } else { 
      cinfo->enable_1pass_quant = TRUE; 
    } 
 
    if (cinfo->enable_1pass_quant) { 
#ifdef QUANT_1PASS_SUPPORTED 
      jinit_1pass_quantizer(cinfo); 
      master->quantizer_1pass = cinfo->cquantize; 
#else 
      ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif 
    } 
 
    /* We use the 2-pass code to map to external colormaps. */ 
    if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) { 
#ifdef QUANT_2PASS_SUPPORTED 
      jinit_2pass_quantizer(cinfo); 
      master->quantizer_2pass = cinfo->cquantize; 
#else 
      ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif 
    } 
    /* If both quantizers are initialized, the 2-pass one is left active; 
     * this is necessary for starting with quantization to an external map. 
     */ 
  } 
 
  /* Post-processing: in particular, color conversion first */ 
  if (! cinfo->raw_data_out) { 
    if (master->using_merged_upsample) { 
#ifdef UPSAMPLE_MERGING_SUPPORTED 
      jinit_merged_upsampler(cinfo); /* does color conversion too */ 
#else 
      ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif 
    } else { 
      jinit_color_deconverter(cinfo); 
      jinit_upsampler(cinfo); 
    } 
    jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant); 
  } 
  /* Inverse DCT */ 
  jinit_inverse_dct(cinfo); 
  /* Entropy decoding: either Huffman or arithmetic coding. */ 
  if (cinfo->arith_code) { 
    ERREXIT(cinfo, JERR_ARITH_NOTIMPL); 
  } else { 
    if (cinfo->progressive_mode) { 
#ifdef D_PROGRESSIVE_SUPPORTED 
      jinit_phuff_decoder(cinfo); 
#else 
      ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif 
    } else 
      jinit_huff_decoder(cinfo); 
  } 
 
  /* Initialize principal buffer controllers. */ 
  use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image; 
  jinit_d_coef_controller(cinfo, use_c_buffer); 
 
  if (! cinfo->raw_data_out) 
    jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */); 
 
  /* We can now tell the memory manager to allocate virtual arrays. */ 
  (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo); 
 
  /* Initialize input side of decompressor to consume first scan. */ 
  (*cinfo->inputctl->start_input_pass) (cinfo); 
 
#ifdef D_MULTISCAN_FILES_SUPPORTED 
  /* If jpeg_start_decompress will read the whole file, initialize 
   * progress monitoring appropriately.  The input step is counted 
   * as one pass. 
   */ 
  if (cinfo->progress != NULL && ! cinfo->buffered_image && 
      cinfo->inputctl->has_multiple_scans) { 
    int nscans; 
    /* Estimate number of scans to set pass_limit. */ 
    if (cinfo->progressive_mode) { 
      /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */ 
      nscans = 2 + 3 * cinfo->num_components; 
    } else { 
      /* For a nonprogressive multiscan file, estimate 1 scan per component. */ 
      nscans = cinfo->num_components; 
    } 
    cinfo->progress->pass_counter = 0L; 
    cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans; 
    cinfo->progress->completed_passes = 0; 
    cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2); 
    /* Count the input pass as done */ 
    master->pass_number++; 
  } 
#endif /* D_MULTISCAN_FILES_SUPPORTED */ 
} 
 
 
/* 
 * Per-pass setup. 
 * This is called at the beginning of each output pass.  We determine which 
 * modules will be active during this pass and give them appropriate 
 * start_pass calls.  We also set is_dummy_pass to indicate whether this 
 * is a "real" output pass or a dummy pass for color quantization. 
 * (In the latter case, jdapistd.c will crank the pass to completion.) 
 */ 
 
METHODDEF(void) 
prepare_for_output_pass (j_decompress_ptr cinfo) 
{ 
  my_master_ptr master = (my_master_ptr) cinfo->master; 
 
  if (master->pub.is_dummy_pass) { 
#ifdef QUANT_2PASS_SUPPORTED 
    /* Final pass of 2-pass quantization */ 
    master->pub.is_dummy_pass = FALSE; 
    (*cinfo->cquantize->start_pass) (cinfo, FALSE); 
    (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST); 
    (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST); 
#else 
    ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif /* QUANT_2PASS_SUPPORTED */ 
  } else { 
    if (cinfo->quantize_colors && cinfo->colormap == NULL) { 
      /* Select new quantization method */ 
      if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) { 
	cinfo->cquantize = master->quantizer_2pass; 
	master->pub.is_dummy_pass = TRUE; 
      } else if (cinfo->enable_1pass_quant) { 
	cinfo->cquantize = master->quantizer_1pass; 
      } else { 
	ERREXIT(cinfo, JERR_MODE_CHANGE); 
      } 
    } 
    (*cinfo->idct->start_pass) (cinfo); 
    (*cinfo->coef->start_output_pass) (cinfo); 
    if (! cinfo->raw_data_out) { 
      if (! master->using_merged_upsample) 
	(*cinfo->cconvert->start_pass) (cinfo); 
      (*cinfo->upsample->start_pass) (cinfo); 
      if (cinfo->quantize_colors) 
	(*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass); 
      (*cinfo->post->start_pass) (cinfo, 
	    (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU)); 
      (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU); 
    } 
  } 
 
  /* Set up progress monitor's pass info if present */ 
  if (cinfo->progress != NULL) { 
    cinfo->progress->completed_passes = master->pass_number; 
    cinfo->progress->total_passes = master->pass_number + 
				    (master->pub.is_dummy_pass ? 2 : 1); 
    /* In buffered-image mode, we assume one more output pass if EOI not 
     * yet reached, but no more passes if EOI has been reached. 
     */ 
    if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) { 
      cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1); 
    } 
  } 
} 
 
 
/* 
 * Finish up at end of an output pass. 
 */ 
 
METHODDEF(void) 
finish_output_pass (j_decompress_ptr cinfo) 
{ 
  my_master_ptr master = (my_master_ptr) cinfo->master; 
 
  if (cinfo->quantize_colors) 
    (*cinfo->cquantize->finish_pass) (cinfo); 
  master->pass_number++; 
} 
 
 
#ifdef D_MULTISCAN_FILES_SUPPORTED 
 
/* 
 * Switch to a new external colormap between output passes. 
 */ 
 
GLOBAL(void) 
jpeg_new_colormap (j_decompress_ptr cinfo) 
{ 
  my_master_ptr master = (my_master_ptr) cinfo->master; 
 
  /* Prevent application from calling me at wrong times */ 
  if (cinfo->global_state != DSTATE_BUFIMAGE) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
 
  if (cinfo->quantize_colors && cinfo->enable_external_quant && 
      cinfo->colormap != NULL) { 
    /* Select 2-pass quantizer for external colormap use */ 
    cinfo->cquantize = master->quantizer_2pass; 
    /* Notify quantizer of colormap change */ 
    (*cinfo->cquantize->new_color_map) (cinfo); 
    master->pub.is_dummy_pass = FALSE; /* just in case */ 
  } else 
    ERREXIT(cinfo, JERR_MODE_CHANGE); 
} 
 
#endif /* D_MULTISCAN_FILES_SUPPORTED */ 
 
 
/* 
 * Initialize master decompression control and select active modules. 
 * This is performed at the start of jpeg_start_decompress. 
 */ 
 
GLOBAL(void) 
jinit_master_decompress (j_decompress_ptr cinfo) 
{ 
  my_master_ptr master; 
 
  master = (my_master_ptr) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				  SIZEOF(my_decomp_master)); 
  cinfo->master = (struct jpeg_decomp_master *) master; 
  master->pub.prepare_for_output_pass = prepare_for_output_pass; 
  master->pub.finish_output_pass = finish_output_pass; 
 
  master->pub.is_dummy_pass = FALSE; 
 
  master_selection(cinfo); 
}