jdmaster.c

一套图像处理程序,支持三种图像文件格式,我调试过了,很好用

/*
 * jdmaster.c
 *
 * Copyright (C) 1991-1994, 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 enum {
	main_pass,		/* read and process a single-scan file */
	preread_pass,		/* read one scan of a multi-scan file */
	output_pass,		/* primary processing pass for multi-scan */
	post_pass		/* optional post-pass for 2-pass quant. */
} D_PASS_TYPE;

typedef struct {
  struct jpeg_decomp_master pub; /* public fields */

  boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */

  D_PASS_TYPE pass_type;	/* the type of the current pass */

  int pass_number;		/* # of passes completed */
  int total_passes;		/* estimated total # of passes needed */

  boolean need_post_pass;	/* are we using full two-pass quantization? */
} 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 */
  /* by golly, it'll work... */
  return TRUE;
#else
  return FALSE;
#endif
}


/*
 * Support routines that do various essential calculations.
 *
 * jpeg_calc_output_dimensions is exported for possible use by application.
 * Hence it mustn't do anything that can't be done twice.
 */

GLOBAL void
jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
/* Do computations that are needed before master selection phase */
{
  int ci;
  jpeg_component_info *compptr;

  /* Compute maximum sampling factors; check factor validity */
  cinfo->max_h_samp_factor = 1;
  cinfo->max_v_samp_factor = 1;
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR ||
	compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR)
      ERREXIT(cinfo, JERR_BAD_SAMPLING);
    cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor,
				   compptr->h_samp_factor);
    cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor,
				   compptr->v_samp_factor);
  }

  /* Compute actual output image dimensions and DCT scaling choices. */
#ifdef IDCT_SCALING_SUPPORTED
  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;
  }
#else /* !IDCT_SCALING_SUPPORTED */
  /* Hardwire it to "no scaling" */
  cinfo->output_width = cinfo->image_width;
  cinfo->output_height = cinfo->image_height;
  cinfo->min_DCT_scaled_size = DCTSIZE;
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    compptr->DCT_scaled_size = DCTSIZE;
  }
#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;

  /* Compute various sampling-related dimensions.
   * Some of these are of interest to the application if it is dealing with
   * "raw" (not upsampled) output, so we do the calculations here.
   */

  /* Compute dimensions of components */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Size in DCT blocks */
    compptr->width_in_blocks = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
		    (long) (cinfo->max_h_samp_factor * DCTSIZE));
    compptr->height_in_blocks = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
		    (long) (cinfo->max_v_samp_factor * DCTSIZE));
    /* 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));
    /* Mark component needed, until color conversion says otherwise */
    compptr->component_needed = TRUE;
  }

  /* Compute number of fully interleaved MCU rows (number of times that
   * main controller will call coefficient controller).
   */
  cinfo->total_iMCU_rows = (JDIMENSION)
    jdiv_round_up((long) cinfo->image_height,
		  (long) (cinfo->max_v_samp_factor*DCTSIZE));
}


LOCAL void
per_scan_setup (j_decompress_ptr cinfo)
/* Do computations that are needed before processing a JPEG scan */
/* cinfo->comps_in_scan and cinfo->cur_comp_info[] were set from SOS marker */
{
  int ci, mcublks, tmp;
  jpeg_component_info *compptr;
  
  if (cinfo->comps_in_scan == 1) {
    
    /* Noninterleaved (single-component) scan */
    compptr = cinfo->cur_comp_info[0];
    
    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = compptr->width_in_blocks;
    cinfo->MCU_rows_in_scan = compptr->height_in_blocks;
    
    /* For noninterleaved scan, always one block per MCU */
    compptr->MCU_width = 1;
    compptr->MCU_height = 1;
    compptr->MCU_blocks = 1;
    compptr->MCU_sample_width = compptr->DCT_scaled_size;
    compptr->last_col_width = 1;
    compptr->last_row_height = 1;
    
    /* Prepare array describing MCU composition */
    cinfo->blocks_in_MCU = 1;
    cinfo->MCU_membership[0] = 0;
    
  } else {
    
    /* Interleaved (multi-component) scan */
    if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
	       MAX_COMPS_IN_SCAN);
    
    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width,
		    (long) (cinfo->max_h_samp_factor*DCTSIZE));
    cinfo->MCU_rows_in_scan = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height,
		    (long) (cinfo->max_v_samp_factor*DCTSIZE));
    
    cinfo->blocks_in_MCU = 0;
    
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      /* Sampling factors give # of blocks of component in each MCU */
      compptr->MCU_width = compptr->h_samp_factor;
      compptr->MCU_height = compptr->v_samp_factor;
      compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
      compptr->MCU_sample_width = compptr->MCU_width * compptr->DCT_scaled_size;
      /* Figure number of non-dummy blocks in last MCU column & row */
      tmp = (int) (compptr->width_in_blocks % compptr->MCU_width);
      if (tmp == 0) tmp = compptr->MCU_width;
      compptr->last_col_width = tmp;
      tmp = (int) (compptr->height_in_blocks % compptr->MCU_height);
      if (tmp == 0) tmp = compptr->MCU_height;
      compptr->last_row_height = tmp;
      /* Prepare array describing MCU composition */
      mcublks = compptr->MCU_blocks;
      if (cinfo->blocks_in_MCU + mcublks > MAX_BLOCKS_IN_MCU)
	ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
      while (mcublks-- > 0) {
	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
      }
    }
    
  }
}


/*
 * 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