1 /*
2 * rdjpgcom.c
3 *
4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1994-1997, Thomas G. Lane.
6 * Modified 2009 by Bill Allombert, Guido Vollbeding.
7 * It was modified by The libjpeg-turbo Project to include only code relevant
8 * to libjpeg-turbo.
9 * For conditions of distribution and use, see the accompanying README.ijg
10 * file.
11 *
12 * This file contains a very simple stand-alone application that displays
13 * the text in COM (comment) markers in a JFIF file.
14 * This may be useful as an example of the minimum logic needed to parse
15 * JPEG markers.
16 */
17
18 #define JPEG_CJPEG_DJPEG /* to get the command-line config symbols */
19 #include "jinclude.h" /* get auto-config symbols, <stdio.h> */
20
21 #ifdef HAVE_LOCALE_H
22 #include <locale.h> /* Bill Allombert: use locale for isprint */
23 #endif
24 #include <ctype.h> /* to declare isupper(), tolower() */
25 #ifdef USE_SETMODE
26 #include <fcntl.h> /* to declare setmode()'s parameter macros */
27 /* If you have setmode() but not <io.h>, just delete this line: */
28 #include <io.h> /* to declare setmode() */
29 #endif
30
31 #ifdef USE_CCOMMAND /* command-line reader for Macintosh */
32 #ifdef __MWERKS__
33 #include <SIOUX.h> /* Metrowerks needs this */
34 #include <console.h> /* ... and this */
35 #endif
36 #ifdef THINK_C
37 #include <console.h> /* Think declares it here */
38 #endif
39 #endif
40
41 #ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */
42 #define READ_BINARY "r"
43 #else
44 #define READ_BINARY "rb"
45 #endif
46
47 #ifndef EXIT_FAILURE /* define exit() codes if not provided */
48 #define EXIT_FAILURE 1
49 #endif
50 #ifndef EXIT_SUCCESS
51 #define EXIT_SUCCESS 0
52 #endif
53
54
55 /*
56 * These macros are used to read the input file.
57 * To reuse this code in another application, you might need to change these.
58 */
59
60 static FILE *infile; /* input JPEG file */
61
62 /* Return next input byte, or EOF if no more */
63 #define NEXTBYTE() getc(infile)
64
65
66 /* Error exit handler */
67 #define ERREXIT(msg) (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE))
68
69
70 /* Read one byte, testing for EOF */
71 static int
read_1_byte(void)72 read_1_byte(void)
73 {
74 int c;
75
76 c = NEXTBYTE();
77 if (c == EOF)
78 ERREXIT("Premature EOF in JPEG file");
79 return c;
80 }
81
82 /* Read 2 bytes, convert to unsigned int */
83 /* All 2-byte quantities in JPEG markers are MSB first */
84 static unsigned int
read_2_bytes(void)85 read_2_bytes(void)
86 {
87 int c1, c2;
88
89 c1 = NEXTBYTE();
90 if (c1 == EOF)
91 ERREXIT("Premature EOF in JPEG file");
92 c2 = NEXTBYTE();
93 if (c2 == EOF)
94 ERREXIT("Premature EOF in JPEG file");
95 return (((unsigned int)c1) << 8) + ((unsigned int)c2);
96 }
97
98
99 /*
100 * JPEG markers consist of one or more 0xFF bytes, followed by a marker
101 * code byte (which is not an FF). Here are the marker codes of interest
102 * in this program. (See jdmarker.c for a more complete list.)
103 */
104
105 #define M_SOF0 0xC0 /* Start Of Frame N */
106 #define M_SOF1 0xC1 /* N indicates which compression process */
107 #define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */
108 #define M_SOF3 0xC3
109 #define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */
110 #define M_SOF6 0xC6
111 #define M_SOF7 0xC7
112 #define M_SOF9 0xC9
113 #define M_SOF10 0xCA
114 #define M_SOF11 0xCB
115 #define M_SOF13 0xCD
116 #define M_SOF14 0xCE
117 #define M_SOF15 0xCF
118 #define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */
119 #define M_EOI 0xD9 /* End Of Image (end of datastream) */
120 #define M_SOS 0xDA /* Start Of Scan (begins compressed data) */
121 #define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */
122 #define M_COM 0xFE /* COMment */
123
124
125 /*
126 * Find the next JPEG marker and return its marker code.
127 * We expect at least one FF byte, possibly more if the compressor used FFs
128 * to pad the file.
129 * There could also be non-FF garbage between markers. The treatment of such
130 * garbage is unspecified; we choose to skip over it but emit a warning msg.
131 * NB: this routine must not be used after seeing SOS marker, since it will
132 * not deal correctly with FF/00 sequences in the compressed image data...
133 */
134
135 static int
next_marker(void)136 next_marker(void)
137 {
138 int c;
139 int discarded_bytes = 0;
140
141 /* Find 0xFF byte; count and skip any non-FFs. */
142 c = read_1_byte();
143 while (c != 0xFF) {
144 discarded_bytes++;
145 c = read_1_byte();
146 }
147 /* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs
148 * are legal as pad bytes, so don't count them in discarded_bytes.
149 */
150 do {
151 c = read_1_byte();
152 } while (c == 0xFF);
153
154 if (discarded_bytes != 0) {
155 fprintf(stderr, "Warning: garbage data found in JPEG file\n");
156 }
157
158 return c;
159 }
160
161
162 /*
163 * Read the initial marker, which should be SOI.
164 * For a JFIF file, the first two bytes of the file should be literally
165 * 0xFF M_SOI. To be more general, we could use next_marker, but if the
166 * input file weren't actually JPEG at all, next_marker might read the whole
167 * file and then return a misleading error message...
168 */
169
170 static int
first_marker(void)171 first_marker(void)
172 {
173 int c1, c2;
174
175 c1 = NEXTBYTE();
176 c2 = NEXTBYTE();
177 if (c1 != 0xFF || c2 != M_SOI)
178 ERREXIT("Not a JPEG file");
179 return c2;
180 }
181
182
183 /*
184 * Most types of marker are followed by a variable-length parameter segment.
185 * This routine skips over the parameters for any marker we don't otherwise
186 * want to process.
187 * Note that we MUST skip the parameter segment explicitly in order not to
188 * be fooled by 0xFF bytes that might appear within the parameter segment;
189 * such bytes do NOT introduce new markers.
190 */
191
192 static void
skip_variable(void)193 skip_variable(void)
194 /* Skip over an unknown or uninteresting variable-length marker */
195 {
196 unsigned int length;
197
198 /* Get the marker parameter length count */
199 length = read_2_bytes();
200 /* Length includes itself, so must be at least 2 */
201 if (length < 2)
202 ERREXIT("Erroneous JPEG marker length");
203 length -= 2;
204 /* Skip over the remaining bytes */
205 while (length > 0) {
206 (void)read_1_byte();
207 length--;
208 }
209 }
210
211
212 /*
213 * Process a COM marker.
214 * We want to print out the marker contents as legible text;
215 * we must guard against non-text junk and varying newline representations.
216 */
217
218 static void
process_COM(int raw)219 process_COM(int raw)
220 {
221 unsigned int length;
222 int ch;
223 int lastch = 0;
224
225 /* Bill Allombert: set locale properly for isprint */
226 #ifdef HAVE_LOCALE_H
227 setlocale(LC_CTYPE, "");
228 #endif
229
230 /* Get the marker parameter length count */
231 length = read_2_bytes();
232 /* Length includes itself, so must be at least 2 */
233 if (length < 2)
234 ERREXIT("Erroneous JPEG marker length");
235 length -= 2;
236
237 while (length > 0) {
238 ch = read_1_byte();
239 if (raw) {
240 putc(ch, stdout);
241 /* Emit the character in a readable form.
242 * Nonprintables are converted to \nnn form,
243 * while \ is converted to \\.
244 * Newlines in CR, CR/LF, or LF form will be printed as one newline.
245 */
246 } else if (ch == '\r') {
247 printf("\n");
248 } else if (ch == '\n') {
249 if (lastch != '\r')
250 printf("\n");
251 } else if (ch == '\\') {
252 printf("\\\\");
253 } else if (isprint(ch)) {
254 putc(ch, stdout);
255 } else {
256 printf("\\%03o", ch);
257 }
258 lastch = ch;
259 length--;
260 }
261 printf("\n");
262
263 /* Bill Allombert: revert to C locale */
264 #ifdef HAVE_LOCALE_H
265 setlocale(LC_CTYPE, "C");
266 #endif
267 }
268
269
270 /*
271 * Process a SOFn marker.
272 * This code is only needed if you want to know the image dimensions...
273 */
274
275 static void
process_SOFn(int marker)276 process_SOFn(int marker)
277 {
278 unsigned int length;
279 unsigned int image_height, image_width;
280 int data_precision, num_components;
281 const char *process;
282 int ci;
283
284 length = read_2_bytes(); /* usual parameter length count */
285
286 data_precision = read_1_byte();
287 image_height = read_2_bytes();
288 image_width = read_2_bytes();
289 num_components = read_1_byte();
290
291 switch (marker) {
292 case M_SOF0: process = "Baseline"; break;
293 case M_SOF1: process = "Extended sequential"; break;
294 case M_SOF2: process = "Progressive"; break;
295 case M_SOF3: process = "Lossless"; break;
296 case M_SOF5: process = "Differential sequential"; break;
297 case M_SOF6: process = "Differential progressive"; break;
298 case M_SOF7: process = "Differential lossless"; break;
299 case M_SOF9: process = "Extended sequential, arithmetic coding"; break;
300 case M_SOF10: process = "Progressive, arithmetic coding"; break;
301 case M_SOF11: process = "Lossless, arithmetic coding"; break;
302 case M_SOF13: process = "Differential sequential, arithmetic coding"; break;
303 case M_SOF14:
304 process = "Differential progressive, arithmetic coding"; break;
305 case M_SOF15: process = "Differential lossless, arithmetic coding"; break;
306 default: process = "Unknown"; break;
307 }
308
309 printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n",
310 image_width, image_height, num_components, data_precision);
311 printf("JPEG process: %s\n", process);
312
313 if (length != (unsigned int)(8 + num_components * 3))
314 ERREXIT("Bogus SOF marker length");
315
316 for (ci = 0; ci < num_components; ci++) {
317 (void)read_1_byte(); /* Component ID code */
318 (void)read_1_byte(); /* H, V sampling factors */
319 (void)read_1_byte(); /* Quantization table number */
320 }
321 }
322
323
324 /*
325 * Parse the marker stream until SOS or EOI is seen;
326 * display any COM markers.
327 * While the companion program wrjpgcom will always insert COM markers before
328 * SOFn, other implementations might not, so we scan to SOS before stopping.
329 * If we were only interested in the image dimensions, we would stop at SOFn.
330 * (Conversely, if we only cared about COM markers, there would be no need
331 * for special code to handle SOFn; we could treat it like other markers.)
332 */
333
334 static int
scan_JPEG_header(int verbose,int raw)335 scan_JPEG_header(int verbose, int raw)
336 {
337 int marker;
338
339 /* Expect SOI at start of file */
340 if (first_marker() != M_SOI)
341 ERREXIT("Expected SOI marker first");
342
343 /* Scan miscellaneous markers until we reach SOS. */
344 for (;;) {
345 marker = next_marker();
346 switch (marker) {
347 /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be,
348 * treated as SOFn. C4 in particular is actually DHT.
349 */
350 case M_SOF0: /* Baseline */
351 case M_SOF1: /* Extended sequential, Huffman */
352 case M_SOF2: /* Progressive, Huffman */
353 case M_SOF3: /* Lossless, Huffman */
354 case M_SOF5: /* Differential sequential, Huffman */
355 case M_SOF6: /* Differential progressive, Huffman */
356 case M_SOF7: /* Differential lossless, Huffman */
357 case M_SOF9: /* Extended sequential, arithmetic */
358 case M_SOF10: /* Progressive, arithmetic */
359 case M_SOF11: /* Lossless, arithmetic */
360 case M_SOF13: /* Differential sequential, arithmetic */
361 case M_SOF14: /* Differential progressive, arithmetic */
362 case M_SOF15: /* Differential lossless, arithmetic */
363 if (verbose)
364 process_SOFn(marker);
365 else
366 skip_variable();
367 break;
368
369 case M_SOS: /* stop before hitting compressed data */
370 return marker;
371
372 case M_EOI: /* in case it's a tables-only JPEG stream */
373 return marker;
374
375 case M_COM:
376 process_COM(raw);
377 break;
378
379 case M_APP12:
380 /* Some digital camera makers put useful textual information into
381 * APP12 markers, so we print those out too when in -verbose mode.
382 */
383 if (verbose) {
384 printf("APP12 contains:\n");
385 process_COM(raw);
386 } else
387 skip_variable();
388 break;
389
390 default: /* Anything else just gets skipped */
391 skip_variable(); /* we assume it has a parameter count... */
392 break;
393 }
394 } /* end loop */
395 }
396
397
398 /* Command line parsing code */
399
400 static const char *progname; /* program name for error messages */
401
402
403 static void
usage(void)404 usage(void)
405 /* complain about bad command line */
406 {
407 fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n");
408
409 fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname);
410
411 fprintf(stderr, "Switches (names may be abbreviated):\n");
412 fprintf(stderr, " -raw Display non-printable characters in comments (unsafe)\n");
413 fprintf(stderr, " -verbose Also display dimensions of JPEG image\n");
414
415 exit(EXIT_FAILURE);
416 }
417
418
419 static int
keymatch(char * arg,const char * keyword,int minchars)420 keymatch(char *arg, const char *keyword, int minchars)
421 /* Case-insensitive matching of (possibly abbreviated) keyword switches. */
422 /* keyword is the constant keyword (must be lower case already), */
423 /* minchars is length of minimum legal abbreviation. */
424 {
425 register int ca, ck;
426 register int nmatched = 0;
427
428 while ((ca = *arg++) != '\0') {
429 if ((ck = *keyword++) == '\0')
430 return 0; /* arg longer than keyword, no good */
431 if (isupper(ca)) /* force arg to lcase (assume ck is already) */
432 ca = tolower(ca);
433 if (ca != ck)
434 return 0; /* no good */
435 nmatched++; /* count matched characters */
436 }
437 /* reached end of argument; fail if it's too short for unique abbrev */
438 if (nmatched < minchars)
439 return 0;
440 return 1; /* A-OK */
441 }
442
443
444 /*
445 * The main program.
446 */
447
448 int
main(int argc,char ** argv)449 main(int argc, char **argv)
450 {
451 int argn;
452 char *arg;
453 int verbose = 0, raw = 0;
454
455 /* On Mac, fetch a command line. */
456 #ifdef USE_CCOMMAND
457 argc = ccommand(&argv);
458 #endif
459
460 progname = argv[0];
461 if (progname == NULL || progname[0] == 0)
462 progname = "rdjpgcom"; /* in case C library doesn't provide it */
463
464 /* Parse switches, if any */
465 for (argn = 1; argn < argc; argn++) {
466 arg = argv[argn];
467 if (arg[0] != '-')
468 break; /* not switch, must be file name */
469 arg++; /* advance over '-' */
470 if (keymatch(arg, "verbose", 1)) {
471 verbose++;
472 } else if (keymatch(arg, "raw", 1)) {
473 raw = 1;
474 } else
475 usage();
476 }
477
478 /* Open the input file. */
479 /* Unix style: expect zero or one file name */
480 if (argn < argc - 1) {
481 fprintf(stderr, "%s: only one input file\n", progname);
482 usage();
483 }
484 if (argn < argc) {
485 if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) {
486 fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
487 exit(EXIT_FAILURE);
488 }
489 } else {
490 /* default input file is stdin */
491 #ifdef USE_SETMODE /* need to hack file mode? */
492 setmode(fileno(stdin), O_BINARY);
493 #endif
494 #ifdef USE_FDOPEN /* need to re-open in binary mode? */
495 if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) {
496 fprintf(stderr, "%s: can't open stdin\n", progname);
497 exit(EXIT_FAILURE);
498 }
499 #else
500 infile = stdin;
501 #endif
502 }
503
504 /* Scan the JPEG headers. */
505 (void)scan_JPEG_header(verbose, raw);
506
507 /* All done. */
508 exit(EXIT_SUCCESS);
509 return 0; /* suppress no-return-value warnings */
510 }
511