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 file. 10 * 11 * This file contains a very simple stand-alone application that displays 12 * the text in COM (comment) markers in a JFIF file. 13 * This may be useful as an example of the minimum logic needed to parse 14 * JPEG markers. 15 */ 16 17 #define JPEG_CJPEG_DJPEG /* to get the command-line config symbols */ 18 #include "jinclude.h" /* get auto-config symbols, <stdio.h> */ 19 20 #ifdef HAVE_LOCALE_H 21 #include <locale.h> /* Bill Allombert: use locale for isprint */ 22 #endif 23 #include <ctype.h> /* to declare isupper(), tolower() */ 24 #ifdef USE_SETMODE 25 #include <fcntl.h> /* to declare setmode()'s parameter macros */ 26 /* If you have setmode() but not <io.h>, just delete this line: */ 27 #include <io.h> /* to declare setmode() */ 28 #endif 29 30 #ifdef USE_CCOMMAND /* command-line reader for Macintosh */ 31 #ifdef __MWERKS__ 32 #include <SIOUX.h> /* Metrowerks needs this */ 33 #include <console.h> /* ... and this */ 34 #endif 35 #ifdef THINK_C 36 #include <console.h> /* Think declares it here */ 37 #endif 38 #endif 39 40 #ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */ 41 #define READ_BINARY "r" 42 #else 43 #define READ_BINARY "rb" 44 #endif 45 46 #ifndef EXIT_FAILURE /* define exit() codes if not provided */ 47 #define EXIT_FAILURE 1 48 #endif 49 #ifndef EXIT_SUCCESS 50 #define EXIT_SUCCESS 0 51 #endif 52 53 54 /* 55 * These macros are used to read the input file. 56 * To reuse this code in another application, you might need to change these. 57 */ 58 59 static FILE * infile; /* input JPEG file */ 60 61 /* Return next input byte, or EOF if no more */ 62 #define NEXTBYTE() getc(infile) 63 64 65 /* Error exit handler */ 66 #define ERREXIT(msg) (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE)) 67 68 69 /* Read one byte, testing for EOF */ 70 static int 71 read_1_byte (void) 72 { 73 int c; 74 75 c = NEXTBYTE(); 76 if (c == EOF) 77 ERREXIT("Premature EOF in JPEG file"); 78 return c; 79 } 80 81 /* Read 2 bytes, convert to unsigned int */ 82 /* All 2-byte quantities in JPEG markers are MSB first */ 83 static unsigned int 84 read_2_bytes (void) 85 { 86 int c1, c2; 87 88 c1 = NEXTBYTE(); 89 if (c1 == EOF) 90 ERREXIT("Premature EOF in JPEG file"); 91 c2 = NEXTBYTE(); 92 if (c2 == EOF) 93 ERREXIT("Premature EOF in JPEG file"); 94 return (((unsigned int) c1) << 8) + ((unsigned int) c2); 95 } 96 97 98 /* 99 * JPEG markers consist of one or more 0xFF bytes, followed by a marker 100 * code byte (which is not an FF). Here are the marker codes of interest 101 * in this program. (See jdmarker.c for a more complete list.) 102 */ 103 104 #define M_SOF0 0xC0 /* Start Of Frame N */ 105 #define M_SOF1 0xC1 /* N indicates which compression process */ 106 #define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */ 107 #define M_SOF3 0xC3 108 #define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */ 109 #define M_SOF6 0xC6 110 #define M_SOF7 0xC7 111 #define M_SOF9 0xC9 112 #define M_SOF10 0xCA 113 #define M_SOF11 0xCB 114 #define M_SOF13 0xCD 115 #define M_SOF14 0xCE 116 #define M_SOF15 0xCF 117 #define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */ 118 #define M_EOI 0xD9 /* End Of Image (end of datastream) */ 119 #define M_SOS 0xDA /* Start Of Scan (begins compressed data) */ 120 #define M_APP0 0xE0 /* Application-specific marker, type N */ 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 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 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 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 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 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: process = "Differential progressive, arithmetic coding"; break; 304 case M_SOF15: process = "Differential lossless, arithmetic coding"; break; 305 default: process = "Unknown"; break; 306 } 307 308 printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n", 309 image_width, image_height, num_components, data_precision); 310 printf("JPEG process: %s\n", process); 311 312 if (length != (unsigned int) (8 + num_components * 3)) 313 ERREXIT("Bogus SOF marker length"); 314 315 for (ci = 0; ci < num_components; ci++) { 316 (void) read_1_byte(); /* Component ID code */ 317 (void) read_1_byte(); /* H, V sampling factors */ 318 (void) read_1_byte(); /* Quantization table number */ 319 } 320 } 321 322 323 /* 324 * Parse the marker stream until SOS or EOI is seen; 325 * display any COM markers. 326 * While the companion program wrjpgcom will always insert COM markers before 327 * SOFn, other implementations might not, so we scan to SOS before stopping. 328 * If we were only interested in the image dimensions, we would stop at SOFn. 329 * (Conversely, if we only cared about COM markers, there would be no need 330 * for special code to handle SOFn; we could treat it like other markers.) 331 */ 332 333 static int 334 scan_JPEG_header (int verbose, int raw) 335 { 336 int marker; 337 338 /* Expect SOI at start of file */ 339 if (first_marker() != M_SOI) 340 ERREXIT("Expected SOI marker first"); 341 342 /* Scan miscellaneous markers until we reach SOS. */ 343 for (;;) { 344 marker = next_marker(); 345 switch (marker) { 346 /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be, 347 * treated as SOFn. C4 in particular is actually DHT. 348 */ 349 case M_SOF0: /* Baseline */ 350 case M_SOF1: /* Extended sequential, Huffman */ 351 case M_SOF2: /* Progressive, Huffman */ 352 case M_SOF3: /* Lossless, Huffman */ 353 case M_SOF5: /* Differential sequential, Huffman */ 354 case M_SOF6: /* Differential progressive, Huffman */ 355 case M_SOF7: /* Differential lossless, Huffman */ 356 case M_SOF9: /* Extended sequential, arithmetic */ 357 case M_SOF10: /* Progressive, arithmetic */ 358 case M_SOF11: /* Lossless, arithmetic */ 359 case M_SOF13: /* Differential sequential, arithmetic */ 360 case M_SOF14: /* Differential progressive, arithmetic */ 361 case M_SOF15: /* Differential lossless, arithmetic */ 362 if (verbose) 363 process_SOFn(marker); 364 else 365 skip_variable(); 366 break; 367 368 case M_SOS: /* stop before hitting compressed data */ 369 return marker; 370 371 case M_EOI: /* in case it's a tables-only JPEG stream */ 372 return marker; 373 374 case M_COM: 375 process_COM(raw); 376 break; 377 378 case M_APP12: 379 /* Some digital camera makers put useful textual information into 380 * APP12 markers, so we print those out too when in -verbose mode. 381 */ 382 if (verbose) { 383 printf("APP12 contains:\n"); 384 process_COM(raw); 385 } else 386 skip_variable(); 387 break; 388 389 default: /* Anything else just gets skipped */ 390 skip_variable(); /* we assume it has a parameter count... */ 391 break; 392 } 393 } /* end loop */ 394 } 395 396 397 /* Command line parsing code */ 398 399 static const char * progname; /* program name for error messages */ 400 401 402 static void 403 usage (void) 404 /* complain about bad command line */ 405 { 406 fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n"); 407 408 fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname); 409 410 fprintf(stderr, "Switches (names may be abbreviated):\n"); 411 fprintf(stderr, " -raw Display non-printable characters in comments (unsafe)\n"); 412 fprintf(stderr, " -verbose Also display dimensions of JPEG image\n"); 413 414 exit(EXIT_FAILURE); 415 } 416 417 418 static int 419 keymatch (char * arg, const char * keyword, int minchars) 420 /* Case-insensitive matching of (possibly abbreviated) keyword switches. */ 421 /* keyword is the constant keyword (must be lower case already), */ 422 /* minchars is length of minimum legal abbreviation. */ 423 { 424 register int ca, ck; 425 register int nmatched = 0; 426 427 while ((ca = *arg++) != '\0') { 428 if ((ck = *keyword++) == '\0') 429 return 0; /* arg longer than keyword, no good */ 430 if (isupper(ca)) /* force arg to lcase (assume ck is already) */ 431 ca = tolower(ca); 432 if (ca != ck) 433 return 0; /* no good */ 434 nmatched++; /* count matched characters */ 435 } 436 /* reached end of argument; fail if it's too short for unique abbrev */ 437 if (nmatched < minchars) 438 return 0; 439 return 1; /* A-OK */ 440 } 441 442 443 /* 444 * The main program. 445 */ 446 447 int 448 main (int argc, char **argv) 449 { 450 int argn; 451 char * arg; 452 int verbose = 0, raw = 0; 453 454 /* On Mac, fetch a command line. */ 455 #ifdef USE_CCOMMAND 456 argc = ccommand(&argv); 457 #endif 458 459 progname = argv[0]; 460 if (progname == NULL || progname[0] == 0) 461 progname = "rdjpgcom"; /* in case C library doesn't provide it */ 462 463 /* Parse switches, if any */ 464 for (argn = 1; argn < argc; argn++) { 465 arg = argv[argn]; 466 if (arg[0] != '-') 467 break; /* not switch, must be file name */ 468 arg++; /* advance over '-' */ 469 if (keymatch(arg, "verbose", 1)) { 470 verbose++; 471 } else if (keymatch(arg, "raw", 1)) { 472 raw = 1; 473 } else 474 usage(); 475 } 476 477 /* Open the input file. */ 478 /* Unix style: expect zero or one file name */ 479 if (argn < argc-1) { 480 fprintf(stderr, "%s: only one input file\n", progname); 481 usage(); 482 } 483 if (argn < argc) { 484 if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) { 485 fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]); 486 exit(EXIT_FAILURE); 487 } 488 } else { 489 /* default input file is stdin */ 490 #ifdef USE_SETMODE /* need to hack file mode? */ 491 setmode(fileno(stdin), O_BINARY); 492 #endif 493 #ifdef USE_FDOPEN /* need to re-open in binary mode? */ 494 if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) { 495 fprintf(stderr, "%s: can't open stdin\n", progname); 496 exit(EXIT_FAILURE); 497 } 498 #else 499 infile = stdin; 500 #endif 501 } 502 503 /* Scan the JPEG headers. */ 504 (void) scan_JPEG_header(verbose, raw); 505 506 /* All done. */ 507 exit(EXIT_SUCCESS); 508 return 0; /* suppress no-return-value warnings */ 509 } 510
