jcapistd.c

基于Linux的ffmepg decoder

/*
 * jcapistd.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 compression half
 * of the JPEG library.  These are the "standard" API routines that are
 * used in the normal full-compression case.  They are not used by a
 * transcoding-only application.  Note that if an application links in
 * jpeg_start_compress, it will end up linking in the entire compressor.
 * We thus must separate this file from jcapimin.c to avoid linking the
 * whole compression library into a transcoder.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/*
 * Compression initialization.
 * Before calling this, all parameters and a data destination must be set up.
 *
 * We require a write_all_tables parameter as a failsafe check when writing
 * multiple datastreams from the same compression object.  Since prior runs
 * will have left all the tables marked sent_table=TRUE, a subsequent run
 * would emit an abbreviated stream (no tables) by default.  This may be what
 * is wanted, but for safety's sake it should not be the default behavior:
 * programmers should have to make a deliberate choice to emit abbreviated
 * images.  Therefore the documentation and examples should encourage people
 * to pass write_all_tables=TRUE; then it will take active thought to do the
 * wrong thing.
 */

GLOBAL(void)
jpeg_start_compress (j_compress_ptr cinfo, boolean write_all_tables)
{
  if (cinfo->global_state != CSTATE_START)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  if (write_all_tables)
    jpeg_suppress_tables(cinfo, FALSE);	/* mark all tables to be written */

  /* (Re)initialize error mgr and destination modules */
  (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
//  (*cinfo->dest->init_destination) (cinfo);				//pwhsu:20031013 init_destination()
  /* Perform master selection of active modules */
  jinit_compress_master(cinfo);				//<---- KEY STEP pwhsu:20031014
											//write file header 20031106
  /* Set up for the first pass */
  (*cinfo->master->prepare_for_pass) (cinfo);			//pwhsu:20031013 prepare_for_pass()
  /* Ready for application to drive first pass through jpeg_write_scanlines
   * or jpeg_write_raw_data.
   */
  cinfo->next_scanline = 0;
  cinfo->global_state = (cinfo->raw_data_in ? CSTATE_RAW_OK : CSTATE_SCANNING); //pwhsu:20031014 
																				//cinfo->global_state = CSTATE_SCANNING
}

/*
 * Write some scanlines of data to the JPEG compressor.
 *
 * The return value will be the number of lines actually written.
 * This should be less than the supplied num_lines only in case that
 * the data destination module has requested suspension of the compressor,
 * or if more than image_height scanlines are passed in.
 *
 * Note: we warn about excess calls to jpeg_write_scanlines() since
 * this likely signals an application programmer error.  However,
 * excess scanlines passed in the last valid call are *silently* ignored,
 * so that the application need not adjust num_lines for end-of-image
 * when using a multiple-scanline buffer.
 */
 

GLOBAL(JDIMENSION)  
jpeg_write_scanlines1 (j_compress_ptr cinfo)
{
  JDIMENSION row_ctr, rows_left;	

  if (cinfo->global_state != CSTATE_SCANNING)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
//  if (cinfo->next_scanline >= cinfo->image_height)
//    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);

#if 0
  //pwhsu:20031015	cinfo->progress=NULL
  /* Call progress monitor hook if present */
  if (cinfo->progress != NULL) {
    cinfo->progress->pass_counter = (long) cinfo->next_scanline;
    cinfo->progress->pass_limit = (long) cinfo->image_height;
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
  }
#endif
  /* Give master control module another chance if this is first call to
   * jpeg_write_scanlines.  This lets output of the frame/scan headers be
   * delayed so that application can write COM, etc, markers between
   * jpeg_start_compress and jpeg_write_scanlines.
   */
  if (cinfo->master->call_pass_startup)
    (*cinfo->master->pass_startup) (cinfo);			//pwhsu:20031015 pass_startup()
													//write frame_header and scan_header 

  /* Ignore any extra scanlines at bottom of image. */
  //rows_left = cinfo->image_height - cinfo->next_scanline;
 // if (num_lines > rows_left)   //pwhsu:20031015 num_lines=1 always smaller than rows_left
 //  num_lines = rows_left;


  row_ctr = 0;
  process_data_simple_main1 (cinfo, &row_ctr);
													
  cinfo->next_scanline += row_ctr;
  return row_ctr;
}