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src/Source/LibJPEG/rdjpgcom.c  view on Meta::CPAN

/*
 * rdjpgcom.c
 *
 * Copyright (C) 1994-1997, Thomas G. Lane.
 * Modified 2009 by Bill Allombert, Guido Vollbeding.
 * 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 a very simple stand-alone application that displays
 * the text in COM (comment) markers in a JFIF file.
 * This may be useful as an example of the minimum logic needed to parse
 * JPEG markers.
 */

#define JPEG_CJPEG_DJPEG	/* to get the command-line config symbols */
#include "jinclude.h"		/* get auto-config symbols, <stdio.h> */

#ifdef HAVE_LOCALE_H
#include <locale.h>		/* Bill Allombert: use locale for isprint */
#endif
#include <ctype.h>		/* to declare isupper(), tolower() */
#ifdef USE_SETMODE
#include <fcntl.h>		/* to declare setmode()'s parameter macros */
/* If you have setmode() but not <io.h>, just delete this line: */
#include <io.h>			/* to declare setmode() */
#endif

#ifdef USE_CCOMMAND		/* command-line reader for Macintosh */
#ifdef __MWERKS__
#include <SIOUX.h>              /* Metrowerks needs this */
#include <console.h>		/* ... and this */
#endif
#ifdef THINK_C
#include <console.h>		/* Think declares it here */
#endif
#endif

#ifdef DONT_USE_B_MODE		/* define mode parameters for fopen() */
#define READ_BINARY	"r"
#else
#ifdef VMS			/* VMS is very nonstandard */
#define READ_BINARY	"rb", "ctx=stm"
#else				/* standard ANSI-compliant case */
#define READ_BINARY	"rb"
#endif
#endif

#ifndef EXIT_FAILURE		/* define exit() codes if not provided */
#define EXIT_FAILURE  1
#endif
#ifndef EXIT_SUCCESS
#ifdef VMS
#define EXIT_SUCCESS  1		/* VMS is very nonstandard */
#else
#define EXIT_SUCCESS  0
#endif
#endif


/*
 * These macros are used to read the input file.
 * To reuse this code in another application, you might need to change these.
 */

static FILE * infile;		/* input JPEG file */

/* Return next input byte, or EOF if no more */
#define NEXTBYTE()  getc(infile)


/* Error exit handler */
#define ERREXIT(msg)  (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE))


/* Read one byte, testing for EOF */
static int
read_1_byte (void)
{
  int c;

src/Source/LibJPEG/rdjpgcom.c  view on Meta::CPAN

 * 0xFF M_SOI.  To be more general, we could use next_marker, but if the
 * input file weren't actually JPEG at all, next_marker might read the whole
 * file and then return a misleading error message...
 */

static int
first_marker (void)
{
  int c1, c2;

  c1 = NEXTBYTE();
  c2 = NEXTBYTE();
  if (c1 != 0xFF || c2 != M_SOI)
    ERREXIT("Not a JPEG file");
  return c2;
}


/*
 * Most types of marker are followed by a variable-length parameter segment.
 * This routine skips over the parameters for any marker we don't otherwise
 * want to process.
 * Note that we MUST skip the parameter segment explicitly in order not to
 * be fooled by 0xFF bytes that might appear within the parameter segment;
 * such bytes do NOT introduce new markers.
 */

static void
skip_variable (void)
/* Skip over an unknown or uninteresting variable-length marker */
{
  unsigned int length;

  /* Get the marker parameter length count */
  length = read_2_bytes();
  /* Length includes itself, so must be at least 2 */
  if (length < 2)
    ERREXIT("Erroneous JPEG marker length");
  length -= 2;
  /* Skip over the remaining bytes */
  while (length > 0) {
    (void) read_1_byte();
    length--;
  }
}


/*
 * Process a COM marker.
 * We want to print out the marker contents as legible text;
 * we must guard against non-text junk and varying newline representations.
 */

static void
process_COM (int raw)
{
  unsigned int length;
  int ch;
  int lastch = 0;

  /* Bill Allombert: set locale properly for isprint */
#ifdef HAVE_LOCALE_H
  setlocale(LC_CTYPE, "");
#endif

  /* Get the marker parameter length count */
  length = read_2_bytes();
  /* Length includes itself, so must be at least 2 */
  if (length < 2)
    ERREXIT("Erroneous JPEG marker length");
  length -= 2;

  while (length > 0) {
    ch = read_1_byte();
    if (raw) {
      putc(ch, stdout);
    /* 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.
     */
    } else if (ch == '\r') {
      printf("\n");
    } else if (ch == '\n') {
      if (lastch != '\r')
	printf("\n");
    } else if (ch == '\\') {
      printf("\\\\");
    } else if (isprint(ch)) {
      putc(ch, stdout);
    } else {
      printf("\\%03o", ch);
    }
    lastch = ch;
    length--;
  }
  printf("\n");

  /* Bill Allombert: revert to C locale */
#ifdef HAVE_LOCALE_H
  setlocale(LC_CTYPE, "C");
#endif
}


/*
 * Process a SOFn marker.
 * This code is only needed if you want to know the image dimensions...
 */

static void
process_SOFn (int marker)
{
  unsigned int length;
  unsigned int image_height, image_width;
  int data_precision, num_components;
  const char * process;
  int ci;

  length = read_2_bytes();	/* usual parameter length count */

  data_precision = read_1_byte();
  image_height = read_2_bytes();
  image_width = read_2_bytes();
  num_components = read_1_byte();

  switch (marker) {
  case M_SOF0:	process = "Baseline";  break;
  case M_SOF1:	process = "Extended sequential";  break;
  case M_SOF2:	process = "Progressive";  break;
  case M_SOF3:	process = "Lossless";  break;
  case M_SOF5:	process = "Differential sequential";  break;
  case M_SOF6:	process = "Differential progressive";  break;
  case M_SOF7:	process = "Differential lossless";  break;
  case M_SOF9:	process = "Extended sequential, arithmetic coding";  break;
  case M_SOF10:	process = "Progressive, arithmetic coding";  break;
  case M_SOF11:	process = "Lossless, arithmetic coding";  break;
  case M_SOF13:	process = "Differential sequential, arithmetic coding";  break;
  case M_SOF14:	process = "Differential progressive, arithmetic coding"; break;
  case M_SOF15:	process = "Differential lossless, arithmetic coding";  break;
  default:	process = "Unknown";  break;
  }

  printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n",
	 image_width, image_height, num_components, data_precision);
  printf("JPEG process: %s\n", process);

  if (length != (unsigned int) (8 + num_components * 3))
    ERREXIT("Bogus SOF marker length");

  for (ci = 0; ci < num_components; ci++) {
    (void) read_1_byte();	/* Component ID code */
    (void) read_1_byte();	/* H, V sampling factors */
    (void) read_1_byte();	/* Quantization table number */
  }
}


/*
 * Parse the marker stream until SOS or EOI is seen;
 * display any COM markers.