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_APP0 0xE0 /* Application-specific marker, type N */
122 #define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */
123 #define M_COM 0xFE /* COMment */
124
125
126 /*
127 * Find the next JPEG marker and return its marker code.
128 * We expect at least one FF byte, possibly more if the compressor used FFs
129 * to pad the file.
130 * There could also be non-FF garbage between markers. The treatment of such
131 * garbage is unspecified; we choose to skip over it but emit a warning msg.
132 * NB: this routine must not be used after seeing SOS marker, since it will
133 * not deal correctly with FF/00 sequences in the compressed image data...
134 */
135
136 static int
next_marker(void)137 next_marker(void)
138 {
139 int c;
140 int discarded_bytes = 0;
141
142 /* Find 0xFF byte; count and skip any non-FFs. */
143 c = read_1_byte();
144 while (c != 0xFF) {
145 discarded_bytes++;
146 c = read_1_byte();
147 }
148 /* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs
149 * are legal as pad bytes, so don't count them in discarded_bytes.
150 */
151 do {
152 c = read_1_byte();
153 } while (c == 0xFF);
154
155 if (discarded_bytes != 0) {
156 fprintf(stderr, "Warning: garbage data found in JPEG file\n");
157 }
158
159 return c;
160 }
161
162
163 /*
164 * Read the initial marker, which should be SOI.
165 * For a JFIF file, the first two bytes of the file should be literally
166 * 0xFF M_SOI. To be more general, we could use next_marker, but if the
167 * input file weren't actually JPEG at all, next_marker might read the whole
168 * file and then return a misleading error message...
169 */
170
171 static int
first_marker(void)172 first_marker(void)
173 {
174 int c1, c2;
175
176 c1 = NEXTBYTE();
177 c2 = NEXTBYTE();
178 if (c1 != 0xFF || c2 != M_SOI)
179 ERREXIT("Not a JPEG file");
180 return c2;
181 }
182
183
184 /*
185 * Most types of marker are followed by a variable-length parameter segment.
186 * This routine skips over the parameters for any marker we don't otherwise
187 * want to process.
188 * Note that we MUST skip the parameter segment explicitly in order not to
189 * be fooled by 0xFF bytes that might appear within the parameter segment;
190 * such bytes do NOT introduce new markers.
191 */
192
193 static void
skip_variable(void)194 skip_variable(void)
195 /* Skip over an unknown or uninteresting variable-length marker */
196 {
197 unsigned int length;
198
199 /* Get the marker parameter length count */
200 length = read_2_bytes();
201 /* Length includes itself, so must be at least 2 */
202 if (length < 2)
203 ERREXIT("Erroneous JPEG marker length");
204 length -= 2;
205 /* Skip over the remaining bytes */
206 while (length > 0) {
207 (void)read_1_byte();
208 length--;
209 }
210 }
211
212
213 /*
214 * Process a COM marker.
215 * We want to print out the marker contents as legible text;
216 * we must guard against non-text junk and varying newline representations.
217 */
218
219 static void
process_COM(int raw)220 process_COM(int raw)
221 {
222 unsigned int length;
223 int ch;
224 int lastch = 0;
225
226 /* Bill Allombert: set locale properly for isprint */
227 #ifdef HAVE_LOCALE_H
228 setlocale(LC_CTYPE, "");
229 #endif
230
231 /* Get the marker parameter length count */
232 length = read_2_bytes();
233 /* Length includes itself, so must be at least 2 */
234 if (length < 2)
235 ERREXIT("Erroneous JPEG marker length");
236 length -= 2;
237
238 while (length > 0) {
239 ch = read_1_byte();
240 if (raw) {
241 putc(ch, stdout);
242 /* Emit the character in a readable form.
243 * Nonprintables are converted to \nnn form,
244 * while \ is converted to \\.
245 * Newlines in CR, CR/LF, or LF form will be printed as one newline.
246 */
247 } else if (ch == '\r') {
248 printf("\n");
249 } else if (ch == '\n') {
250 if (lastch != '\r')
251 printf("\n");
252 } else if (ch == '\\') {
253 printf("\\\\");
254 } else if (isprint(ch)) {
255 putc(ch, stdout);
256 } else {
257 printf("\\%03o", ch);
258 }
259 lastch = ch;
260 length--;
261 }
262 printf("\n");
263
264 /* Bill Allombert: revert to C locale */
265 #ifdef HAVE_LOCALE_H
266 setlocale(LC_CTYPE, "C");
267 #endif
268 }
269
270
271 /*
272 * Process a SOFn marker.
273 * This code is only needed if you want to know the image dimensions...
274 */
275
276 static void
process_SOFn(int marker)277 process_SOFn(int marker)
278 {
279 unsigned int length;
280 unsigned int image_height, image_width;
281 int data_precision, num_components;
282 const char *process;
283 int ci;
284
285 length = read_2_bytes(); /* usual parameter length count */
286
287 data_precision = read_1_byte();
288 image_height = read_2_bytes();
289 image_width = read_2_bytes();
290 num_components = read_1_byte();
291
292 switch (marker) {
293 case M_SOF0: process = "Baseline"; break;
294 case M_SOF1: process = "Extended sequential"; break;
295 case M_SOF2: process = "Progressive"; break;
296 case M_SOF3: process = "Lossless"; break;
297 case M_SOF5: process = "Differential sequential"; break;
298 case M_SOF6: process = "Differential progressive"; break;
299 case M_SOF7: process = "Differential lossless"; break;
300 case M_SOF9: process = "Extended sequential, arithmetic coding"; break;
301 case M_SOF10: process = "Progressive, arithmetic coding"; break;
302 case M_SOF11: process = "Lossless, arithmetic coding"; break;
303 case M_SOF13: process = "Differential sequential, arithmetic coding"; break;
304 case M_SOF14:
305 process = "Differential progressive, arithmetic coding"; break;
306 case M_SOF15: process = "Differential lossless, arithmetic coding"; break;
307 default: process = "Unknown"; break;
308 }
309
310 printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n",
311 image_width, image_height, num_components, data_precision);
312 printf("JPEG process: %s\n", process);
313
314 if (length != (unsigned int)(8 + num_components * 3))
315 ERREXIT("Bogus SOF marker length");
316
317 for (ci = 0; ci < num_components; ci++) {
318 (void)read_1_byte(); /* Component ID code */
319 (void)read_1_byte(); /* H, V sampling factors */
320 (void)read_1_byte(); /* Quantization table number */
321 }
322 }
323
324
325 /*
326 * Parse the marker stream until SOS or EOI is seen;
327 * display any COM markers.
328 * While the companion program wrjpgcom will always insert COM markers before
329 * SOFn, other implementations might not, so we scan to SOS before stopping.
330 * If we were only interested in the image dimensions, we would stop at SOFn.
331 * (Conversely, if we only cared about COM markers, there would be no need
332 * for special code to handle SOFn; we could treat it like other markers.)
333 */
334
335 static int
scan_JPEG_header(int verbose,int raw)336 scan_JPEG_header(int verbose, int raw)
337 {
338 int marker;
339
340 /* Expect SOI at start of file */
341 if (first_marker() != M_SOI)
342 ERREXIT("Expected SOI marker first");
343
344 /* Scan miscellaneous markers until we reach SOS. */
345 for (;;) {
346 marker = next_marker();
347 switch (marker) {
348 /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be,
349 * treated as SOFn. C4 in particular is actually DHT.
350 */
351 case M_SOF0: /* Baseline */
352 case M_SOF1: /* Extended sequential, Huffman */
353 case M_SOF2: /* Progressive, Huffman */
354 case M_SOF3: /* Lossless, Huffman */
355 case M_SOF5: /* Differential sequential, Huffman */
356 case M_SOF6: /* Differential progressive, Huffman */
357 case M_SOF7: /* Differential lossless, Huffman */
358 case M_SOF9: /* Extended sequential, arithmetic */
359 case M_SOF10: /* Progressive, arithmetic */
360 case M_SOF11: /* Lossless, arithmetic */
361 case M_SOF13: /* Differential sequential, arithmetic */
362 case M_SOF14: /* Differential progressive, arithmetic */
363 case M_SOF15: /* Differential lossless, arithmetic */
364 if (verbose)
365 process_SOFn(marker);
366 else
367 skip_variable();
368 break;
369
370 case M_SOS: /* stop before hitting compressed data */
371 return marker;
372
373 case M_EOI: /* in case it's a tables-only JPEG stream */
374 return marker;
375
376 case M_COM:
377 process_COM(raw);
378 break;
379
380 case M_APP12:
381 /* Some digital camera makers put useful textual information into
382 * APP12 markers, so we print those out too when in -verbose mode.
383 */
384 if (verbose) {
385 printf("APP12 contains:\n");
386 process_COM(raw);
387 } else
388 skip_variable();
389 break;
390
391 default: /* Anything else just gets skipped */
392 skip_variable(); /* we assume it has a parameter count... */
393 break;
394 }
395 } /* end loop */
396 }
397
398
399 /* Command line parsing code */
400
401 static const char *progname; /* program name for error messages */
402
403
404 static void
usage(void)405 usage(void)
406 /* complain about bad command line */
407 {
408 fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n");
409
410 fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname);
411
412 fprintf(stderr, "Switches (names may be abbreviated):\n");
413 fprintf(stderr, " -raw Display non-printable characters in comments (unsafe)\n");
414 fprintf(stderr, " -verbose Also display dimensions of JPEG image\n");
415
416 exit(EXIT_FAILURE);
417 }
418
419
420 static int
keymatch(char * arg,const char * keyword,int minchars)421 keymatch(char *arg, const char *keyword, int minchars)
422 /* Case-insensitive matching of (possibly abbreviated) keyword switches. */
423 /* keyword is the constant keyword (must be lower case already), */
424 /* minchars is length of minimum legal abbreviation. */
425 {
426 register int ca, ck;
427 register int nmatched = 0;
428
429 while ((ca = *arg++) != '\0') {
430 if ((ck = *keyword++) == '\0')
431 return 0; /* arg longer than keyword, no good */
432 if (isupper(ca)) /* force arg to lcase (assume ck is already) */
433 ca = tolower(ca);
434 if (ca != ck)
435 return 0; /* no good */
436 nmatched++; /* count matched characters */
437 }
438 /* reached end of argument; fail if it's too short for unique abbrev */
439 if (nmatched < minchars)
440 return 0;
441 return 1; /* A-OK */
442 }
443
444
445 /*
446 * The main program.
447 */
448
449 int
main(int argc,char ** argv)450 main(int argc, char **argv)
451 {
452 int argn;
453 char *arg;
454 int verbose = 0, raw = 0;
455
456 /* On Mac, fetch a command line. */
457 #ifdef USE_CCOMMAND
458 argc = ccommand(&argv);
459 #endif
460
461 progname = argv[0];
462 if (progname == NULL || progname[0] == 0)
463 progname = "rdjpgcom"; /* in case C library doesn't provide it */
464
465 /* Parse switches, if any */
466 for (argn = 1; argn < argc; argn++) {
467 arg = argv[argn];
468 if (arg[0] != '-')
469 break; /* not switch, must be file name */
470 arg++; /* advance over '-' */
471 if (keymatch(arg, "verbose", 1)) {
472 verbose++;
473 } else if (keymatch(arg, "raw", 1)) {
474 raw = 1;
475 } else
476 usage();
477 }
478
479 /* Open the input file. */
480 /* Unix style: expect zero or one file name */
481 if (argn < argc - 1) {
482 fprintf(stderr, "%s: only one input file\n", progname);
483 usage();
484 }
485 if (argn < argc) {
486 if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) {
487 fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
488 exit(EXIT_FAILURE);
489 }
490 } else {
491 /* default input file is stdin */
492 #ifdef USE_SETMODE /* need to hack file mode? */
493 setmode(fileno(stdin), O_BINARY);
494 #endif
495 #ifdef USE_FDOPEN /* need to re-open in binary mode? */
496 if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) {
497 fprintf(stderr, "%s: can't open stdin\n", progname);
498 exit(EXIT_FAILURE);
499 }
500 #else
501 infile = stdin;
502 #endif
503 }
504
505 /* Scan the JPEG headers. */
506 (void)scan_JPEG_header(verbose, raw);
507
508 /* All done. */
509 exit(EXIT_SUCCESS);
510 return 0; /* suppress no-return-value warnings */
511 }
512