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 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 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 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 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 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 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 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: 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 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 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 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 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
