/*

* 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;

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);

}

/*

* 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_APP0 0xE0 /* Application-specific marker, type N */

#define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */

#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.

* 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

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.

* While the companion program wrjpgcom will always insert COM markers before

* SOFn, other implementations might not, so we scan to SOS before stopping.

* If we were only interested in the image dimensions, we would stop at SOFn.

* (Conversely, if we only cared about COM markers, there would be no need

* for special code to handle SOFn; we could treat it like other markers.)

*/

static int

scan_JPEG_header (int verbose, int raw)

{

int marker;

/* Expect SOI at start of file */

if (first_marker() != M_SOI)

ERREXIT("Expected SOI marker first");

/* Scan miscellaneous markers until we reach SOS. */

for (;;) {

marker = next_marker();

switch (marker) {

/* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be,

* treated as SOFn. C4 in particular is actually DHT.

*/

case M_SOF0: /* Baseline */

case M_SOF1: /* Extended sequential, Huffman */

case M_SOF2: /* Progressive, Huffman */

case M_SOF3: /* Lossless, Huffman */

case M_SOF5: /* Differential sequential, Huffman */

case M_SOF6: /* Differential progressive, Huffman */

case M_SOF7: /* Differential lossless, Huffman */

case M_SOF9: /* Extended sequential, arithmetic */

case M_SOF10: /* Progressive, arithmetic */

case M_SOF11: /* Lossless, arithmetic */

case M_SOF13: /* Differential sequential, arithmetic */

case M_SOF14: /* Differential progressive, arithmetic */

case M_SOF15: /* Differential lossless, arithmetic */

if (verbose)

process_SOFn(marker);

else

skip_variable();

break;

case M_SOS: /* stop before hitting compressed data */

return marker;

case M_EOI: /* in case it's a tables-only JPEG stream */

return marker;

case M_COM:

process_COM(raw);

break;

case M_APP12:

/* Some digital camera makers put useful textual information into

* APP12 markers, so we print those out too when in -verbose mode.

*/

if (verbose) {

printf("APP12 contains:\n");

process_COM(raw);

} else

skip_variable();

break;

default: /* Anything else just gets skipped */

skip_variable(); /* we assume it has a parameter count... */

break;

}

} /* end loop */

}

/* Command line parsing code */

static const char * progname; /* program name for error messages */

static void

usage (void)

/* complain about bad command line */

{

fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n");

fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname);

fprintf(stderr, "Switches (names may be abbreviated):\n");

fprintf(stderr, " -raw Display non-printable characters in comments (unsafe)\n");

fprintf(stderr, " -verbose Also display dimensions of JPEG image\n");

exit(EXIT_FAILURE);

}

static int

keymatch (char * arg, const char * keyword, int minchars)

/* Case-insensitive matching of (possibly abbreviated) keyword switches. */

/* keyword is the constant keyword (must be lower case already), */

/* minchars is length of minimum legal abbreviation. */

{

register int ca, ck;

register int nmatched = 0;

while ((ca = *arg++) != '\0') {

if ((ck = *keyword++) == '\0')

return 0; /* arg longer than keyword, no good */

if (isupper(ca)) /* force arg to lcase (assume ck is already) */

ca = tolower(ca);

if (ca != ck)

return 0; /* no good */

nmatched++; /* count matched characters */

}

/* reached end of argument; fail if it's too short for unique abbrev */

if (nmatched < minchars)

return 0;

return 1; /* A-OK */

}

/*

* The main program.

*/

int

main (int argc, char **argv)

{

int argn;

char * arg;

int verbose = 0, raw = 0;

/* On Mac, fetch a command line. */

#ifdef USE_CCOMMAND

argc = ccommand(&argv);

#endif

progname = argv[0];

if (progname == NULL || progname[0] == 0)

progname = "rdjpgcom"; /* in case C library doesn't provide it */

/* Parse switches, if any */

for (argn = 1; argn < argc; argn++) {

arg = argv[argn];

if (arg[0] != '-')

break; /* not switch, must be file name */

arg++; /* advance over '-' */

if (keymatch(arg, "verbose", 1)) {

verbose++;

} else if (keymatch(arg, "raw", 1)) {

raw = 1;

} else

usage();

}

/* Open the input file. */

/* Unix style: expect zero or one file name */

if (argn < argc-1) {

fprintf(stderr, "%s: only one input file\n", progname);

usage();

}

if (argn < argc) {

if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) {

fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);

exit(EXIT_FAILURE);

}

} else {

/* default input file is stdin */

#ifdef USE_SETMODE /* need to hack file mode? */

setmode(fileno(stdin), O_BINARY);

#endif

#ifdef USE_FDOPEN /* need to re-open in binary mode? */

if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) {

fprintf(stderr, "%s: can't open stdin\n", progname);

exit(EXIT_FAILURE);

}

#else

infile = stdin;

#endif

}

/* Scan the JPEG headers. */

(void) scan_JPEG_header(verbose, raw);

/* All done. */

exit(EXIT_SUCCESS);

return 0; /* suppress no-return-value warnings */

}