www.pudn.com > imgport.rar > jdapistd.c, change:2008-11-05,size:9623b


/* 
 * jdapistd.c 
 * 
 * Copyright (C) 1994-1996, 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 application interface code for the decompression half 
 * of the JPEG library.  These are the "standard" API routines that are 
 * used in the normal full-decompression case.  They are not used by a 
 * transcoding-only application.  Note that if an application links in 
 * jpeg_start_decompress, it will end up linking in the entire decompressor. 
 * We thus must separate this file from jdapimin.c to avoid linking the 
 * whole decompression library into a transcoder. 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
 
/* Forward declarations */ 
LOCAL(boolean) output_pass_setup JPP((j_decompress_ptr cinfo)); 
 
 
/* 
 * Decompression initialization. 
 * jpeg_read_header must be completed before calling this. 
 * 
 * If a multipass operating mode was selected, this will do all but the 
 * last pass, and thus may take a great deal of time. 
 * 
 * Returns FALSE if suspended.  The return value need be inspected only if 
 * a suspending data source is used. 
 */ 
 
GLOBAL(boolean) 
jpeg_start_decompress (j_decompress_ptr cinfo) 
{ 
  if (cinfo->global_state == DSTATE_READY) { 
    /* First call: initialize master control, select active modules */ 
    jinit_master_decompress(cinfo); 
    if (cinfo->buffered_image) { 
      /* No more work here; expecting jpeg_start_output next */ 
      cinfo->global_state = DSTATE_BUFIMAGE; 
      return TRUE; 
    } 
    cinfo->global_state = DSTATE_PRELOAD; 
  } 
  if (cinfo->global_state == DSTATE_PRELOAD) { 
    /* If file has multiple scans, absorb them all into the coef buffer */ 
    if (cinfo->inputctl->has_multiple_scans) { 
#ifdef D_MULTISCAN_FILES_SUPPORTED 
      for (;;) { 
	int retcode; 
	/* Call progress monitor hook if present */ 
	if (cinfo->progress != NULL) 
	  (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 
	/* Absorb some more input */ 
	retcode = (*cinfo->inputctl->consume_input) (cinfo); 
	if (retcode == JPEG_SUSPENDED) 
	  return FALSE; 
	if (retcode == JPEG_REACHED_EOI) 
	  break; 
	/* Advance progress counter if appropriate */ 
	if (cinfo->progress != NULL && 
	    (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { 
	  if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { 
	    /* jdmaster underestimated number of scans; ratchet up one scan */ 
	    cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows; 
	  } 
	} 
      } 
#else 
      ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif /* D_MULTISCAN_FILES_SUPPORTED */ 
    } 
    cinfo->output_scan_number = cinfo->input_scan_number; 
  } else if (cinfo->global_state != DSTATE_PRESCAN) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  /* Perform any dummy output passes, and set up for the final pass */ 
  return output_pass_setup(cinfo); 
} 
 
 
/* 
 * Set up for an output pass, and perform any dummy pass(es) needed. 
 * Common subroutine for jpeg_start_decompress and jpeg_start_output. 
 * Entry: global_state = DSTATE_PRESCAN only if previously suspended. 
 * Exit: If done, returns TRUE and sets global_state for proper output mode. 
 *       If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN. 
 */ 
 
LOCAL(boolean) 
output_pass_setup (j_decompress_ptr cinfo) 
{ 
  if (cinfo->global_state != DSTATE_PRESCAN) { 
    /* First call: do pass setup */ 
    (*cinfo->master->prepare_for_output_pass) (cinfo); 
    cinfo->output_scanline = 0; 
    cinfo->global_state = DSTATE_PRESCAN; 
  } 
  /* Loop over any required dummy passes */ 
  while (cinfo->master->is_dummy_pass) { 
#ifdef QUANT_2PASS_SUPPORTED 
    /* Crank through the dummy pass */ 
    while (cinfo->output_scanline < cinfo->output_height) { 
      JDIMENSION last_scanline; 
      /* Call progress monitor hook if present */ 
      if (cinfo->progress != NULL) { 
	cinfo->progress->pass_counter = (long) cinfo->output_scanline; 
	cinfo->progress->pass_limit = (long) cinfo->output_height; 
	(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 
      } 
      /* Process some data */ 
      last_scanline = cinfo->output_scanline; 
      (*cinfo->main->process_data) (cinfo, (JSAMPARRAY) NULL, 
				    &cinfo->output_scanline, (JDIMENSION) 0); 
      if (cinfo->output_scanline == last_scanline) 
	return FALSE;		/* No progress made, must suspend */ 
    } 
    /* Finish up dummy pass, and set up for another one */ 
    (*cinfo->master->finish_output_pass) (cinfo); 
    (*cinfo->master->prepare_for_output_pass) (cinfo); 
    cinfo->output_scanline = 0; 
#else 
    ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif /* QUANT_2PASS_SUPPORTED */ 
  } 
  /* Ready for application to drive output pass through 
   * jpeg_read_scanlines or jpeg_read_raw_data. 
   */ 
  cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING; 
  return TRUE; 
} 
 
 
/* 
 * Read some scanlines of data from the JPEG decompressor. 
 * 
 * The return value will be the number of lines actually read. 
 * This may be less than the number requested in several cases, 
 * including bottom of image, data source suspension, and operating 
 * modes that emit multiple scanlines at a time. 
 * 
 * Note: we warn about excess calls to jpeg_read_scanlines() since 
 * this likely signals an application programmer error.  However, 
 * an oversize buffer (max_lines > scanlines remaining) is not an error. 
 */ 
 
GLOBAL(JDIMENSION) 
jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines, 
		     JDIMENSION max_lines) 
{ 
  JDIMENSION row_ctr; 
 
  if (cinfo->global_state != DSTATE_SCANNING) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  if (cinfo->output_scanline >= cinfo->output_height) { 
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA); 
    return 0; 
  } 
 
  /* Call progress monitor hook if present */ 
  if (cinfo->progress != NULL) { 
    cinfo->progress->pass_counter = (long) cinfo->output_scanline; 
    cinfo->progress->pass_limit = (long) cinfo->output_height; 
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 
  } 
 
  /* Process some data */ 
  row_ctr = 0; 
  (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines); 
  cinfo->output_scanline += row_ctr; 
  return row_ctr; 
} 
 
 
/* 
 * Alternate entry point to read raw data. 
 * Processes exactly one iMCU row per call, unless suspended. 
 */ 
 
GLOBAL(JDIMENSION) 
jpeg_read_raw_data (j_decompress_ptr cinfo, JSAMPIMAGE data, 
		    JDIMENSION max_lines) 
{ 
  JDIMENSION lines_per_iMCU_row; 
 
  if (cinfo->global_state != DSTATE_RAW_OK) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  if (cinfo->output_scanline >= cinfo->output_height) { 
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA); 
    return 0; 
  } 
 
  /* Call progress monitor hook if present */ 
  if (cinfo->progress != NULL) { 
    cinfo->progress->pass_counter = (long) cinfo->output_scanline; 
    cinfo->progress->pass_limit = (long) cinfo->output_height; 
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 
  } 
 
  /* Verify that at least one iMCU row can be returned. */ 
  lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size; 
  if (max_lines < lines_per_iMCU_row) 
    ERREXIT(cinfo, JERR_BUFFER_SIZE); 
 
  /* Decompress directly into user's buffer. */ 
  if (! (*cinfo->coef->decompress_data) (cinfo, data)) 
    return 0;			/* suspension forced, can do nothing more */ 
 
  /* OK, we processed one iMCU row. */ 
  cinfo->output_scanline += lines_per_iMCU_row; 
  return lines_per_iMCU_row; 
} 
 
 
/* Additional entry points for buffered-image mode. */ 
 
#ifdef D_MULTISCAN_FILES_SUPPORTED 
 
/* 
 * Initialize for an output pass in buffered-image mode. 
 */ 
 
GLOBAL(boolean) 
jpeg_start_output (j_decompress_ptr cinfo, int scan_number) 
{ 
  if (cinfo->global_state != DSTATE_BUFIMAGE && 
      cinfo->global_state != DSTATE_PRESCAN) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  /* Limit scan number to valid range */ 
  if (scan_number <= 0) 
    scan_number = 1; 
  if (cinfo->inputctl->eoi_reached && 
      scan_number > cinfo->input_scan_number) 
    scan_number = cinfo->input_scan_number; 
  cinfo->output_scan_number = scan_number; 
  /* Perform any dummy output passes, and set up for the real pass */ 
  return output_pass_setup(cinfo); 
} 
 
 
/* 
 * Finish up after an output pass in buffered-image mode. 
 * 
 * Returns FALSE if suspended.  The return value need be inspected only if 
 * a suspending data source is used. 
 */ 
 
GLOBAL(boolean) 
jpeg_finish_output (j_decompress_ptr cinfo) 
{ 
  if ((cinfo->global_state == DSTATE_SCANNING || 
       cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) { 
    /* Terminate this pass. */ 
    /* We do not require the whole pass to have been completed. */ 
    (*cinfo->master->finish_output_pass) (cinfo); 
    cinfo->global_state = DSTATE_BUFPOST; 
  } else if (cinfo->global_state != DSTATE_BUFPOST) { 
    /* BUFPOST = repeat call after a suspension, anything else is error */ 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  } 
  /* Read markers looking for SOS or EOI */ 
  while (cinfo->input_scan_number <= cinfo->output_scan_number && 
	 ! cinfo->inputctl->eoi_reached) { 
    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED) 
      return FALSE;		/* Suspend, come back later */ 
  } 
  cinfo->global_state = DSTATE_BUFIMAGE; 
  return TRUE; 
} 
 
#endif /* D_MULTISCAN_FILES_SUPPORTED */