wrjpgcom.c

linux下的jpeg解码库

/*
 * wrjpgcom.c
 *
 * Copyright (C) 1994-1997, 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.
 *
 * This file contains a very simple stand-alone application that inserts
 * user-supplied text as a COM (comment) marker 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> */

#ifndef HAVE_STDLIB_H		/* <stdlib.h> should declare malloc() */
extern void * malloc ();
#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"
#define WRITE_BINARY	"w"
#else
#ifdef VMS			/* VMS is very nonstandard */
#define READ_BINARY	"rb", "ctx=stm"
#define WRITE_BINARY	"wb", "ctx=stm"
#else				/* standard ANSI-compliant case */
#define READ_BINARY	"rb"
#define WRITE_BINARY	"wb"
#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

/* Reduce this value if your malloc() can't allocate blocks up to 64K.
 * On DOS, compiling in large model is usually a better solution.
 */

#ifndef MAX_COM_LENGTH
#define MAX_COM_LENGTH 65000L	/* must be <= 65533 in any case */
#endif


/*
 * These macros are used to read the input file and write the output 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)

static FILE * outfile;		/* output JPEG file */

/* Emit an output byte */
#define PUTBYTE(x)  putc((x), outfile)


/* 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;

  c = NEXTBYTE();
  if (c == EOF)
    ERREXIT("Premature EOF in JPEG file");
  return c;
}

/* Read 2 bytes, convert to unsigned int */
/* All 2-byte quantities in JPEG markers are MSB first */
static unsigned int
read_2_bytes (void)
{
  int c1, c2;

  c1 = NEXTBYTE();
  if (c1 == EOF)
    ERREXIT("Premature EOF in JPEG file");
  c2 = NEXTBYTE();
  if (c2 == EOF)
    ERREXIT("Premature EOF in JPEG file");
  return (((unsigned int) c1) << 8) + ((unsigned int) c2);
}


/* Routines to write data to output file */

static void
write_1_byte (int c)
{
  PUTBYTE(c);
}

static void
write_2_bytes (unsigned int val)
{
  PUTBYTE((val >> 8) & 0xFF);
  PUTBYTE(val & 0xFF);
}

static void
write_marker (int marker)
{
  PUTBYTE(0xFF);
  PUTBYTE(marker);
}

static void
copy_rest_of_file (void)
{
  int c;

  while ((c = NEXTBYTE()) != EOF)
    PUTBYTE(c);
}


/*
 * JPEG markers consist of one or more 0xFF bytes, followed by a marker
 * code byte (which is not an FF).  Here are the marker codes of interest
 * in this program.  (See jdmarker.c for a more complete list.)
 */

#define M_SOF0  0xC0		/* Start Of Frame N */
#define M_SOF1  0xC1		/* N indicates which compression process */
#define M_SOF2  0xC2		/* Only SOF0-SOF2 are now in common use */
#define M_SOF3  0xC3
#define M_SOF5  0xC5		/* NB: codes C4 and CC are NOT SOF markers */
#define M_SOF6  0xC6
#define M_SOF7  0xC7
#define M_SOF9  0xC9
#define M_SOF10 0xCA
#define M_SOF11 0xCB
#define M_SOF13 0xCD
#define M_SOF14 0xCE
#define M_SOF15 0xCF
#define M_SOI   0xD8		/* Start Of Image (beginning of datastream) */
#define M_EOI   0xD9		/* End Of Image (end of datastream) */
#define M_SOS   0xDA		/* Start Of Scan (begins compressed data) */
#define M_COM   0xFE		/* COMment */


/*
 * Find the next JPEG marker and return its marker code.
 * We expect at least one FF byte, possibly more if the compressor used FFs
 * to pad the file.  (Padding FFs will NOT be replicated in the output file.)
 * There could also be non-FF garbage between markers.  The treatment of such
 * garbage is unspecified; we choose to skip over it but emit a warning msg.
 * NB: this routine must not be used after seeing SOS marker, since it will
 * not deal correctly with FF/00 sequences in the compressed image data...
 */

static int
next_marker (void)
{
  int c;
  int discarded_bytes = 0;

  /* Find 0xFF byte; count and skip any non-FFs. */
  c = read_1_byte();
  while (c != 0xFF) {
    discarded_bytes++;
    c = read_1_byte();
  }
  /* Get marker code byte, swallowing any duplicate FF bytes.  Extra FFs
   * are legal as pad bytes, so don't count them in discarded_bytes.
   */
  do {
    c = read_1_byte();
  } while (c == 0xFF);

  if (discarded_bytes != 0) {
    fprintf(stderr, "Warning: garbage data found in JPEG file\n");
  }

  return c;
}


/*
 * Read the initial marker, which should be SOI.
 * For a JFIF file, the first two bytes of the file should be literally
 * 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
copy_variable (void)
/* Copy an unknown or uninteresting variable-length marker */
{
  unsigned int length;

  /* Get the marker parameter length count */
  length = read_2_bytes();
  write_2_bytes(length);
  /* 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) {
    write_1_byte(read_1_byte());
    length--;
  }
}

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--;
  }
}


/*
 * Parse the marker stream until SOFn or EOI is seen;
 * copy data to output, but discard COM markers unless keep_COM is true.
 */

static int
scan_JPEG_header (int keep_COM)
{
  int marker;