djpeg.c

来自「mp4的源码,主要包括loader,usb driver,mp3 decoder」· C语言 代码 · 共 169 行

/*
 * djpeg.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.
 *
 */

#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */
#include <ctype.h>		/* to declare isprint() */

/* Create the add-on message string table. */

#define JMESSAGE(code,string)	string ,

static const char * const cdjpeg_message_table[] = {
#include "cderror.h"
  NULL
};


/*
 * Marker processor for COM and interesting APPn markers.
 * This replaces the library's built-in processor, which just skips the marker.
 * We want to print out the marker as text, to the extent possible.
 * Note this code relies on a non-suspending data source.
 */

LOCAL(unsigned int)
jpeg_getc (j_decompress_ptr cinfo)
/* Read next byte */
{
  struct jpeg_source_mgr * datasrc = cinfo->src;

  if (datasrc->bytes_in_buffer == 0) {
    if (! (*datasrc->fill_input_buffer) (cinfo))
      ERREXIT(cinfo, JERR_CANT_SUSPEND);
  }
  datasrc->bytes_in_buffer--;
  return GETJOCTET(*datasrc->next_input_byte++);
}


METHODDEF(boolean)
print_text_marker (j_decompress_ptr cinfo)
{
  boolean traceit = (cinfo->err->trace_level >= 1);
  INT32 length;
  unsigned int ch;
  unsigned int lastch = 0;

  length = jpeg_getc(cinfo) << 8;
  length += jpeg_getc(cinfo);
  length -= 2;			/* discount the length word itself */

  if (traceit) {
    if (cinfo->unread_marker == JPEG_COM)
      fprintf(stderr, "Comment, length %ld:\n", (long) length);
    else			/* assume it is an APPn otherwise */
      fprintf(stderr, "APP%d, length %ld:\n",
	      cinfo->unread_marker - JPEG_APP0, (long) length);
  }

  while (--length >= 0) {
    ch = jpeg_getc(cinfo);
    if (traceit) {
      /* Emit the character in a readable form.
       * Nonprintables are converted to \nnn form,
       * while \ is converted to \\.
       * Newlines in CR, CR/LF, or LF form will be printed as one newline.
       */
      if (ch == '\r') {
	fprintf(stderr, "\n");
      } else if (ch == '\n') {
	if (lastch != '\r')
	  fprintf(stderr, "\n");
      } else if (ch == '\\') {
	fprintf(stderr, "\\\\");
      } else if (isprint(ch)) {
	putc(ch, stderr);
      } else {
	fprintf(stderr, "\\%03o", ch);
      }
      lastch = ch;
    }
  }

  if (traceit)
    fprintf(stderr, "\n");

  return TRUE;
}


/*
 * The main program.
 */

int
djpeg (char * filename)
{
  struct jpeg_decompress_struct cinfo;
  FILE * input_file;
  djpeg_dest_ptr dest_mgr = NULL;
  JDIMENSION num_scanlines;

  jpeg_create_decompress(&cinfo);
 
  /* Insert custom marker processor for COM and APP12.
   * APP12 is used by some digital camera makers for textual info,
   * so we provide the ability to display it as text.
   * If you like, additional APPn marker types can be selected for display,
   * but don't try to override APP0 or APP14 this way (see libjpeg.doc).
   */
  jpeg_set_marker_processor(&cinfo, JPEG_COM, print_text_marker);
  jpeg_set_marker_processor(&cinfo, JPEG_APP0+12, print_text_marker);

  /* Open the input file. */
   if ((input_file = file_open(filename)) == NULL) {
      fprintf(stderr, "file can't open \n");
      exit(EXIT_FAILURE);
    }


  /* Specify data source for decompression */
  jpeg_stdio_src(&cinfo, input_file);

  /* Read file header, set default decompression parameters */
  (void) jpeg_read_header(&cinfo, TRUE);


  /* Initialize the output module now to let it override any crucial
   * option settings (for instance, GIF wants to force color quantization).
   */
  dest_mgr = jinit_write_bmp(&cinfo, FALSE);
  
  dest_mgr->output_file = output_file;

  /* Start decompressor */
  (void) jpeg_start_decompress(&cinfo);

  /* Write output file header */
  (*dest_mgr->start_output) (&cinfo, dest_mgr);

  /* Process data */
  while (cinfo.output_scanline < cinfo.output_height) {
    num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
					dest_mgr->buffer_height);
    (*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
  }


  /* Finish decompression and release memory.
   * I must do it in this order because output module has allocated memory
   * of lifespan JPOOL_IMAGE; it needs to finish before releasing memory.
   */
  (*dest_mgr->finish_output) (&cinfo, dest_mgr);
  (void) jpeg_finish_decompress(&cinfo);
  jpeg_destroy_decompress(&cinfo);

  /* Close files */
  fclose(input_file);

  /* All done. */
  exit(jerr.num_warnings ? EXIT_WARNING : EXIT_SUCCESS);
  return 0;			/* suppress no-return-value warnings */
}