cjpeg.c

jpeg压缩算法源码

#endif

    } else if (keymatch(arg, "quality", 1)) {
      /* Quality factor (quantization table scaling factor). */
      if (++argn >= argc)	/* advance to next argument */
	usage();
      if (sscanf(argv[argn], "%d", &quality) != 1)
	usage();
      /* Change scale factor in case -qtables is present. */
      q_scale_factor = jpeg_quality_scaling(quality);

    } else if (keymatch(arg, "qslots", 2)) {
      /* Quantization table slot numbers. */
      if (++argn >= argc)	/* advance to next argument */
	usage();
      qslotsarg = argv[argn];
      /* Must delay setting qslots until after we have processed any
       * colorspace-determining switches, since jpeg_set_colorspace sets
       * default quant table numbers.
       */

    } else if (keymatch(arg, "qtables", 2)) {
      /* Quantization tables fetched from file. */
      if (++argn >= argc)	/* advance to next argument */
	usage();
      qtablefile = argv[argn];
      /* We postpone actually reading the file in case -quality comes later. */

    } else if (keymatch(arg, "restart", 1)) {
      /* Restart interval in MCU rows (or in MCUs with 'b'). */
      long lval;
      char ch = 'x';

      if (++argn >= argc)	/* advance to next argument */
	usage();
      if (sscanf(argv[argn], "%ld%c", &lval, &ch) < 1)
	usage();
      if (lval < 0 || lval > 65535L)
	usage();
      if (ch == 'b' || ch == 'B') {
	cinfo->restart_interval = (unsigned int) lval;
	cinfo->restart_in_rows = 0; /* else prior '-restart n' overrides me */
      } else {
	cinfo->restart_in_rows = (int) lval;
	/* restart_interval will be computed during startup */
      }

    } else if (keymatch(arg, "sample", 2)) {
      /* Set sampling factors. */
      if (++argn >= argc)	/* advance to next argument */
	usage();
      samplearg = argv[argn];
      /* Must delay setting sample factors until after we have processed any
       * colorspace-determining switches, since jpeg_set_colorspace sets
       * default sampling factors.
       */

    } else if (keymatch(arg, "scans", 2)) {
      /* Set scan script. */
#ifdef C_MULTISCAN_FILES_SUPPORTED
      if (++argn >= argc)	/* advance to next argument */
	usage();
      scansarg = argv[argn];
      /* We must postpone reading the file in case -progressive appears. */
#else
      fprintf(stderr, "%s: sorry, multi-scan output was not compiled\n",
	      progname);
      exit(EXIT_FAILURE);
#endif

    } else if (keymatch(arg, "smooth", 2)) {
      /* Set input smoothing factor. */
      int val;

      if (++argn >= argc)	/* advance to next argument */
	usage();
      if (sscanf(argv[argn], "%d", &val) != 1)
	usage();
      if (val < 0 || val > 100)
	usage();
      cinfo->smoothing_factor = val;

    } else if (keymatch(arg, "targa", 1)) {
      /* Input file is Targa format. */
      is_targa = TRUE;

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

  /* Post-switch-scanning cleanup */

  if (for_real) {

    /* Set quantization tables for selected quality. */
    /* Some or all may be overridden if -qtables is present. */
    jpeg_set_quality(cinfo, quality, force_baseline);

    if (qtablefile != NULL)	/* process -qtables if it was present */
      if (! read_quant_tables(cinfo, qtablefile,
			      q_scale_factor, force_baseline))
	usage();

    if (qslotsarg != NULL)	/* process -qslots if it was present */
      if (! set_quant_slots(cinfo, qslotsarg))
	usage();

    if (samplearg != NULL)	/* process -sample if it was present */
      if (! set_sample_factors(cinfo, samplearg))
	usage();

#ifdef C_PROGRESSIVE_SUPPORTED
    if (simple_progressive)	/* process -progressive; -scans can override */
      jpeg_simple_progression(cinfo);
#endif

#ifdef C_MULTISCAN_FILES_SUPPORTED
    if (scansarg != NULL)	/* process -scans if it was present */
      if (! read_scan_script(cinfo, scansarg))
	usage();
#endif
  }

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


/*
 * 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_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
  char *infilename;
  char workfilename[PATH_MAX];
#ifdef PROGRESS_REPORT
  struct cdjpeg_progress_mgr progress;
#endif
  int file_index;
  cjpeg_source_ptr src_mgr;
  FILE * input_file = NULL;
  FILE * output_file = NULL;
  JDIMENSION num_scanlines;

  /* Initialize the JPEG compression object with default error handling. */
  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_compress(&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;

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

  /* Initialize JPEG parameters.
   * Much of this may be overridden later.
   * In particular, we don't yet know the input file's color space,
   * but we need to provide some value for jpeg_set_defaults() to work.
   */

  cinfo.in_color_space = JCS_RGB; /* arbitrary guess */
  jpeg_set_defaults(&cinfo);

  /* 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.
   */

  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

  /* Figure out the input file format, and set up to read it. */
  src_mgr = select_file_type(&cinfo, input_file);
  src_mgr->input_file = input_file;

  /* Read the input file header to obtain file size & colorspace. */
  (*src_mgr->start_input) (&cinfo, src_mgr);

  /* Now that we know input colorspace, fix colorspace-dependent defaults */
  jpeg_default_colorspace(&cinfo);

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

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

    outfilename = workfilename;
    /* Make outfilename be infilename with .jpg substituted for 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, ".jpg");
  }

  fprintf(stderr, "Compressing %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;
  }

  /* Specify data destination for compression */
  jpeg_stdio_dest(&cinfo, output_file);

  /* Start compressor */
  jpeg_start_compress(&cinfo, TRUE);

  /* Process data */
  while (cinfo.next_scanline < cinfo.image_height) {
    num_scanlines = (*src_mgr->get_pixel_rows) (&cinfo, src_mgr);
    (void) jpeg_write_scanlines(&cinfo, src_mgr->buffer, num_scanlines);
  }

  /* Finish compression and release memory */
  (*src_mgr->finish_input) (&cinfo, src_mgr);
  jpeg_finish_compress(&cinfo);

  /* Clean up and exit */
fail:
  jpeg_destroy_compress(&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 = "cjpeg";		/* DOS tends to be too verbose about argv[0] */
#else
  progname = argv[0];
  if (progname == NULL || progname[0] == 0)
    progname = "cjpeg";		/* 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 */
}