djpeg.c

来自「JPEG解压源码」· C语言 代码 · 共 751 行 · 第 1/2 页

    } else {
      usage();			/* bogus switch */
    }
  }

  return argn;			/* return index of next arg (file name) */
}


/*
 * 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;
}


/*
 * Check for overwrite of an existing file; clear it with user
 */

#ifndef NO_OVERWRITE_CHECK

LOCAL(boolean)
is_write_ok (char * outfname)
{
  FILE * ofile;
  int ch;

  ofile = fopen(outfname, READ_BINARY);
  if (ofile == NULL)
    return TRUE;		/* not present */
  fclose(ofile);		/* oops, it is present */

  for (;;) {
    fprintf(stderr, "%s already exists, overwrite it? [y/n] ",
	    outfname);
    fflush(stderr);
    ch = getc(stdin);
    if (ch != '\n')		/* flush rest of line */
      while (getc(stdin) != '\n')
	/* nothing */;

    switch (ch) {
    case 'Y':
    case 'y':
      return TRUE;
    case 'N':
    case 'n':
      return FALSE;
    /* otherwise, ask again */
    }
  }
}

#endif


/*
 * Process a single input file name, and return its index in argv[].
 * File names at or to left of old_file_index have been processed already.
 */

LOCAL(int)
process_one_file (int argc, char **argv, int old_file_index)
{
  struct jpeg_decompress_struct cinfo;
  struct jpeg_error_mgr jerr;
  char *infilename;
  char workfilename[PATH_MAX];
  const char *default_extension = NULL;
#ifdef PROGRESS_REPORT
  struct cdjpeg_progress_mgr progress;
#endif
  int file_index;
  djpeg_dest_ptr dest_mgr = NULL;
  FILE * input_file = NULL;
  FILE * output_file = NULL;
  JDIMENSION num_scanlines;

  /* Initialize the JPEG decompression object with default error handling. */
  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_decompress(&cinfo);
  /* Add some application-specific error messages (from cderror.h) */
  jerr.addon_message_table = cdjpeg_message_table;
  jerr.first_addon_message = JMSG_FIRSTADDONCODE;
  jerr.last_addon_message = JMSG_LASTADDONCODE;

  /* 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);

  /* Now safe to enable signal catcher. */
#ifdef NEED_SIGNAL_CATCHER
  enable_signal_catcher((j_common_ptr) &cinfo);
#endif

  /* Scan command line to find next file name.
   * It is convenient to use just one switch-parsing routine, but the switch
   * values read here are ignored; we will rescan the switches after opening
   * the input file.
   * (Exception: tracing level set here controls verbosity for COM markers
   * found during jpeg_read_header...)
   */

  file_index = parse_switches(&cinfo, argc, argv, old_file_index, FALSE);
  if (file_index >= argc) {
    fprintf(stderr, "%s: missing input file name\n", progname);
    usage();
  }

  /* Open the input file. */
  infilename = argv[file_index];
  if ((input_file = fopen(infilename, READ_BINARY)) == NULL) {
    fprintf(stderr, "%s: can't open %s\n", progname, infilename);
    goto fail;
  }

#ifdef PROGRESS_REPORT
  start_progress_monitor((j_common_ptr) &cinfo, &progress);
#endif

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

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

  /* Adjust default decompression parameters by re-parsing the options */
  file_index = parse_switches(&cinfo, argc, argv, old_file_index, TRUE);

  /* Initialize the output module now to let it override any crucial
   * option settings (for instance, GIF wants to force color quantization).
   */
  switch (requested_fmt) {
#ifdef BMP_SUPPORTED
  case FMT_BMP:
    dest_mgr = jinit_write_bmp(&cinfo, FALSE);
    default_extension = ".bmp";
    break;
  case FMT_OS2:
    dest_mgr = jinit_write_bmp(&cinfo, TRUE);
    default_extension = ".bmp";
    break;
#endif
#ifdef GIF_SUPPORTED
  case FMT_GIF:
    dest_mgr = jinit_write_gif(&cinfo);
    default_extension = ".gif";
    break;
#endif
#ifdef PPM_SUPPORTED
  case FMT_PPM:
    dest_mgr = jinit_write_ppm(&cinfo);
    default_extension = ".ppm";
    break;
#endif
#ifdef RLE_SUPPORTED
  case FMT_RLE:
    dest_mgr = jinit_write_rle(&cinfo);
    default_extension = ".rle";
    break;
#endif
#ifdef TARGA_SUPPORTED
  case FMT_TARGA:
    dest_mgr = jinit_write_targa(&cinfo);
    default_extension = ".tga";
    break;
#endif
  default:
    ERREXIT(&cinfo, JERR_UNSUPPORTED_FORMAT);
    break;
  }

  /* If user didn't supply -outfile switch, select output file name. */
  if (outfilename == NULL) {
    int i;

    outfilename = workfilename;
    /* Make outfilename be infilename with appropriate extension */
    strcpy(outfilename, infilename);
    for (i = strlen(outfilename)-1; i >= 0; i--) {
      switch (outfilename[i]) {
      case ':':
      case '/':
      case '\\':
	i = 0;			/* stop scanning */
	break;
      case '.':
	outfilename[i] = '\0';	/* lop off existing extension */
	i = 0;			/* stop scanning */
	break;
      default:
	break;			/* keep scanning */
      }
    }
    strcat(outfilename, default_extension);
  }

  fprintf(stderr, "Decompressing %s => %s\n", infilename, outfilename);
#ifndef NO_OVERWRITE_CHECK
  if (! is_write_ok(outfilename))
    goto fail;
#endif

  /* Open the output file. */
  if ((output_file = fopen(outfilename, WRITE_BINARY)) == NULL) {
    fprintf(stderr, "%s: can't create %s\n", progname, outfilename);
    goto fail;
  }
  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);
  }

#ifdef PROGRESS_REPORT
  /* Hack: count final pass as done in case finish_output does an extra pass.
   * The library won't have updated completed_passes.
   */
  progress.pub.completed_passes = progress.pub.total_passes;
#endif

  /* 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);

  /* Clean up and exit */
fail:
  jpeg_destroy_decompress(&cinfo);

  if (input_file != NULL) fclose(input_file);
  if (output_file != NULL) fclose(output_file);

#ifdef PROGRESS_REPORT
  end_progress_monitor((j_common_ptr) &cinfo);
#endif

  /* Disable signal catcher. */
#ifdef NEED_SIGNAL_CATCHER
  enable_signal_catcher((j_common_ptr) NULL);
#endif

  return file_index;
}


/*
 * The main program.
 */

int
main (int argc, char **argv)
{
  int file_index;

  /* On Mac, fetch a command line. */
#ifdef USE_CCOMMAND
  argc = ccommand(&argv);
#endif

#ifdef MSDOS
  progname = "djpeg";		/* DOS tends to be too verbose about argv[0] */
#else
  progname = argv[0];
  if (progname == NULL || progname[0] == 0)
    progname = "djpeg";		/* in case C library doesn't provide it */
#endif

  /* The default maxmem must be computed only once at program startup,
   * since releasing memory with free() won't give it back to the OS.
   */
#ifdef FREE_MEM_ESTIMATE
  default_maxmem = FREE_MEM_ESTIMATE;
#else
  default_maxmem = 0;
#endif

  /* Scan command line, parse switches and locate input file names */

  if (argc < 2)
    usage();			/* nothing on the command line?? */

  file_index = 0;

  while (file_index < argc-1)
    file_index = process_one_file(argc, argv, file_index);

  /* All done. */
  exit(EXIT_SUCCESS);
  return 0;			/* suppress no-return-value warnings */
}