1 /* 2 * rdjpgcom.c 3 * 4 * Copyright (C) 1994-1997, Thomas G. Lane. 5 * This file is part of the Independent JPEG Group's software. 6 * For conditions of distribution and use, see the accompanying README file. 7 * 8 * This file contains a very simple stand-alone application that displays 9 * the text in COM (comment) markers in a JFIF file. 10 * This may be useful as an example of the minimum logic needed to parse 11 * JPEG markers. 12 */ 13 14 #define JPEG_CJPEG_DJPEG /* to get the command-line config symbols */ 15 #include "jinclude.h" /* get auto-config symbols, <stdio.h> */ 16 17 #include <ctype.h> /* to declare isupper(), tolower() */ 18 #ifdef USE_SETMODE 19 #include <fcntl.h> /* to declare setmode()'s parameter macros */ 20 /* If you have setmode() but not <io.h>, just delete this line: */ 21 #include <io.h> /* to declare setmode() */ 22 #endif 23 24 #ifdef USE_CCOMMAND /* command-line reader for Macintosh */ 25 #ifdef __MWERKS__ 26 #include <SIOUX.h> /* Metrowerks needs this */ 27 #include <console.h> /* ... and this */ 28 #endif 29 #ifdef THINK_C 30 #include <console.h> /* Think declares it here */ 31 #endif 32 #endif 33 34 #ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */ 35 #define READ_BINARY "r" 36 #else 37 #ifdef VMS /* VMS is very nonstandard */ 38 #define READ_BINARY "rb", "ctx=stm" 39 #else /* standard ANSI-compliant case */ 40 #define READ_BINARY "rb" 41 #endif 42 #endif 43 44 #ifndef EXIT_FAILURE /* define exit() codes if not provided */ 45 #define EXIT_FAILURE 1 46 #endif 47 #ifndef EXIT_SUCCESS 48 #ifdef VMS 49 #define EXIT_SUCCESS 1 /* VMS is very nonstandard */ 50 #else 51 #define EXIT_SUCCESS 0 52 #endif 53 #endif 54 55 56 /* 57 * These macros are used to read the input file. 58 * To reuse this code in another application, you might need to change these. 59 */ 60 61 static FILE * infile; /* input JPEG file */ 62 63 /* Return next input byte, or EOF if no more */ 64 #define NEXTBYTE() getc(infile) 65 66 67 /* Error exit handler */ 68 #define ERREXIT(msg) (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE)) 69 70 71 /* Read one byte, testing for EOF */ 72 static int 73 read_1_byte (void) 74 { 75 int c; 76 77 c = NEXTBYTE(); 78 if (c == EOF) 79 ERREXIT("Premature EOF in JPEG file"); 80 return c; 81 } 82 83 /* Read 2 bytes, convert to unsigned int */ 84 /* All 2-byte quantities in JPEG markers are MSB first */ 85 static unsigned int 86 read_2_bytes (void) 87 { 88 int c1, c2; 89 90 c1 = NEXTBYTE(); 91 if (c1 == EOF) 92 ERREXIT("Premature EOF in JPEG file"); 93 c2 = NEXTBYTE(); 94 if (c2 == EOF) 95 ERREXIT("Premature EOF in JPEG file"); 96 return (((unsigned int) c1) << 8) + ((unsigned int) c2); 97 } 98 99 100 /* 101 * JPEG markers consist of one or more 0xFF bytes, followed by a marker 102 * code byte (which is not an FF). Here are the marker codes of interest 103 * in this program. (See jdmarker.c for a more complete list.) 104 */ 105 106 #define M_SOF0 0xC0 /* Start Of Frame N */ 107 #define M_SOF1 0xC1 /* N indicates which compression process */ 108 #define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */ 109 #define M_SOF3 0xC3 110 #define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */ 111 #define M_SOF6 0xC6 112 #define M_SOF7 0xC7 113 #define M_SOF9 0xC9 114 #define M_SOF10 0xCA 115 #define M_SOF11 0xCB 116 #define M_SOF13 0xCD 117 #define M_SOF14 0xCE 118 #define M_SOF15 0xCF 119 #define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */ 120 #define M_EOI 0xD9 /* End Of Image (end of datastream) */ 121 #define M_SOS 0xDA /* Start Of Scan (begins compressed data) */ 122 #define M_APP0 0xE0 /* Application-specific marker, type N */ 123 #define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */ 124 #define M_COM 0xFE /* COMment */ 125 126 127 /* 128 * Find the next JPEG marker and return its marker code. 129 * We expect at least one FF byte, possibly more if the compressor used FFs 130 * to pad the file. 131 * There could also be non-FF garbage between markers. The treatment of such 132 * garbage is unspecified; we choose to skip over it but emit a warning msg. 133 * NB: this routine must not be used after seeing SOS marker, since it will 134 * not deal correctly with FF/00 sequences in the compressed image data... 135 */ 136 137 static int 138 next_marker (void) 139 { 140 int c; 141 int discarded_bytes = 0; 142 143 /* Find 0xFF byte; count and skip any non-FFs. */ 144 c = read_1_byte(); 145 while (c != 0xFF) { 146 discarded_bytes++; 147 c = read_1_byte(); 148 } 149 /* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs 150 * are legal as pad bytes, so don't count them in discarded_bytes. 151 */ 152 do { 153 c = read_1_byte(); 154 } while (c == 0xFF); 155 156 if (discarded_bytes != 0) { 157 fprintf(stderr, "Warning: garbage data found in JPEG file\n"); 158 } 159 160 return c; 161 } 162 163 164 /* 165 * Read the initial marker, which should be SOI. 166 * For a JFIF file, the first two bytes of the file should be literally 167 * 0xFF M_SOI. To be more general, we could use next_marker, but if the 168 * input file weren't actually JPEG at all, next_marker might read the whole 169 * file and then return a misleading error message... 170 */ 171 172 static int 173 first_marker (void) 174 { 175 int c1, c2; 176 177 c1 = NEXTBYTE(); 178 c2 = NEXTBYTE(); 179 if (c1 != 0xFF || c2 != M_SOI) 180 ERREXIT("Not a JPEG file"); 181 return c2; 182 } 183 184 185 /* 186 * Most types of marker are followed by a variable-length parameter segment. 187 * This routine skips over the parameters for any marker we don't otherwise 188 * want to process. 189 * Note that we MUST skip the parameter segment explicitly in order not to 190 * be fooled by 0xFF bytes that might appear within the parameter segment; 191 * such bytes do NOT introduce new markers. 192 */ 193 194 static void 195 skip_variable (void) 196 /* Skip over an unknown or uninteresting variable-length marker */ 197 { 198 unsigned int length; 199 200 /* Get the marker parameter length count */ 201 length = read_2_bytes(); 202 /* Length includes itself, so must be at least 2 */ 203 if (length < 2) 204 ERREXIT("Erroneous JPEG marker length"); 205 length -= 2; 206 /* Skip over the remaining bytes */ 207 while (length > 0) { 208 (void) read_1_byte(); 209 length--; 210 } 211 } 212 213 214 /* 215 * Process a COM marker. 216 * We want to print out the marker contents as legible text; 217 * we must guard against non-text junk and varying newline representations. 218 */ 219 220 static void 221 process_COM (void) 222 { 223 unsigned int length; 224 int ch; 225 int lastch = 0; 226 227 /* Get the marker parameter length count */ 228 length = read_2_bytes(); 229 /* Length includes itself, so must be at least 2 */ 230 if (length < 2) 231 ERREXIT("Erroneous JPEG marker length"); 232 length -= 2; 233 234 while (length > 0) { 235 ch = read_1_byte(); 236 /* Emit the character in a readable form. 237 * Nonprintables are converted to \nnn form, 238 * while \ is converted to \\. 239 * Newlines in CR, CR/LF, or LF form will be printed as one newline. 240 */ 241 if (ch == '\r') { 242 printf("\n"); 243 } else if (ch == '\n') { 244 if (lastch != '\r') 245 printf("\n"); 246 } else if (ch == '\\') { 247 printf("\\\\"); 248 } else if (isprint(ch)) { 249 putc(ch, stdout); 250 } else { 251 printf("\\%03o", ch); 252 } 253 lastch = ch; 254 length--; 255 } 256 printf("\n"); 257 } 258 259 260 /* 261 * Process a SOFn marker. 262 * This code is only needed if you want to know the image dimensions... 263 */ 264 265 static void 266 process_SOFn (int marker) 267 { 268 unsigned int length; 269 unsigned int image_height, image_width; 270 int data_precision, num_components; 271 const char * process; 272 int ci; 273 274 length = read_2_bytes(); /* usual parameter length count */ 275 276 data_precision = read_1_byte(); 277 image_height = read_2_bytes(); 278 image_width = read_2_bytes(); 279 num_components = read_1_byte(); 280 281 switch (marker) { 282 case M_SOF0: process = "Baseline"; break; 283 case M_SOF1: process = "Extended sequential"; break; 284 case M_SOF2: process = "Progressive"; break; 285 case M_SOF3: process = "Lossless"; break; 286 case M_SOF5: process = "Differential sequential"; break; 287 case M_SOF6: process = "Differential progressive"; break; 288 case M_SOF7: process = "Differential lossless"; break; 289 case M_SOF9: process = "Extended sequential, arithmetic coding"; break; 290 case M_SOF10: process = "Progressive, arithmetic coding"; break; 291 case M_SOF11: process = "Lossless, arithmetic coding"; break; 292 case M_SOF13: process = "Differential sequential, arithmetic coding"; break; 293 case M_SOF14: process = "Differential progressive, arithmetic coding"; break; 294 case M_SOF15: process = "Differential lossless, arithmetic coding"; break; 295 default: process = "Unknown"; break; 296 } 297 298 printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n", 299 image_width, image_height, num_components, data_precision); 300 printf("JPEG process: %s\n", process); 301 302 if (length != (unsigned int) (8 + num_components * 3)) 303 ERREXIT("Bogus SOF marker length"); 304 305 for (ci = 0; ci < num_components; ci++) { 306 (void) read_1_byte(); /* Component ID code */ 307 (void) read_1_byte(); /* H, V sampling factors */ 308 (void) read_1_byte(); /* Quantization table number */ 309 } 310 } 311 312 313 /* 314 * Parse the marker stream until SOS or EOI is seen; 315 * display any COM markers. 316 * While the companion program wrjpgcom will always insert COM markers before 317 * SOFn, other implementations might not, so we scan to SOS before stopping. 318 * If we were only interested in the image dimensions, we would stop at SOFn. 319 * (Conversely, if we only cared about COM markers, there would be no need 320 * for special code to handle SOFn; we could treat it like other markers.) 321 */ 322 323 static int 324 scan_JPEG_header (int verbose) 325 { 326 int marker; 327 328 /* Expect SOI at start of file */ 329 if (first_marker() != M_SOI) 330 ERREXIT("Expected SOI marker first"); 331 332 /* Scan miscellaneous markers until we reach SOS. */ 333 for (;;) { 334 marker = next_marker(); 335 switch (marker) { 336 /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be, 337 * treated as SOFn. C4 in particular is actually DHT. 338 */ 339 case M_SOF0: /* Baseline */ 340 case M_SOF1: /* Extended sequential, Huffman */ 341 case M_SOF2: /* Progressive, Huffman */ 342 case M_SOF3: /* Lossless, Huffman */ 343 case M_SOF5: /* Differential sequential, Huffman */ 344 case M_SOF6: /* Differential progressive, Huffman */ 345 case M_SOF7: /* Differential lossless, Huffman */ 346 case M_SOF9: /* Extended sequential, arithmetic */ 347 case M_SOF10: /* Progressive, arithmetic */ 348 case M_SOF11: /* Lossless, arithmetic */ 349 case M_SOF13: /* Differential sequential, arithmetic */ 350 case M_SOF14: /* Differential progressive, arithmetic */ 351 case M_SOF15: /* Differential lossless, arithmetic */ 352 if (verbose) 353 process_SOFn(marker); 354 else 355 skip_variable(); 356 break; 357 358 case M_SOS: /* stop before hitting compressed data */ 359 return marker; 360 361 case M_EOI: /* in case it's a tables-only JPEG stream */ 362 return marker; 363 364 case M_COM: 365 process_COM(); 366 break; 367 368 case M_APP12: 369 /* Some digital camera makers put useful textual information into 370 * APP12 markers, so we print those out too when in -verbose mode. 371 */ 372 if (verbose) { 373 printf("APP12 contains:\n"); 374 process_COM(); 375 } else 376 skip_variable(); 377 break; 378 379 default: /* Anything else just gets skipped */ 380 skip_variable(); /* we assume it has a parameter count... */ 381 break; 382 } 383 } /* end loop */ 384 } 385 386 387 /* Command line parsing code */ 388 389 static const char * progname; /* program name for error messages */ 390 391 392 static void 393 usage (void) 394 /* complain about bad command line */ 395 { 396 fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n"); 397 398 fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname); 399 400 fprintf(stderr, "Switches (names may be abbreviated):\n"); 401 fprintf(stderr, " -verbose Also display dimensions of JPEG image\n"); 402 403 exit(EXIT_FAILURE); 404 } 405 406 407 static int 408 keymatch (char * arg, const char * keyword, int minchars) 409 /* Case-insensitive matching of (possibly abbreviated) keyword switches. */ 410 /* keyword is the constant keyword (must be lower case already), */ 411 /* minchars is length of minimum legal abbreviation. */ 412 { 413 register int ca, ck; 414 register int nmatched = 0; 415 416 while ((ca = *arg++) != '\0') { 417 if ((ck = *keyword++) == '\0') 418 return 0; /* arg longer than keyword, no good */ 419 if (isupper(ca)) /* force arg to lcase (assume ck is already) */ 420 ca = tolower(ca); 421 if (ca != ck) 422 return 0; /* no good */ 423 nmatched++; /* count matched characters */ 424 } 425 /* reached end of argument; fail if it's too short for unique abbrev */ 426 if (nmatched < minchars) 427 return 0; 428 return 1; /* A-OK */ 429 } 430 431 432 /* 433 * The main program. 434 */ 435 436 int 437 main (int argc, char **argv) 438 { 439 int argn; 440 char * arg; 441 int verbose = 0; 442 443 /* On Mac, fetch a command line. */ 444 #ifdef USE_CCOMMAND 445 argc = ccommand(&argv); 446 #endif 447 448 progname = argv[0]; 449 if (progname == NULL || progname[0] == 0) 450 progname = "rdjpgcom"; /* in case C library doesn't provide it */ 451 452 /* Parse switches, if any */ 453 for (argn = 1; argn < argc; argn++) { 454 arg = argv[argn]; 455 if (arg[0] != '-') 456 break; /* not switch, must be file name */ 457 arg++; /* advance over '-' */ 458 if (keymatch(arg, "verbose", 1)) { 459 verbose++; 460 } else 461 usage(); 462 } 463 464 /* Open the input file. */ 465 /* Unix style: expect zero or one file name */ 466 if (argn < argc-1) { 467 fprintf(stderr, "%s: only one input file\n", progname); 468 usage(); 469 } 470 if (argn < argc) { 471 if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) { 472 fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]); 473 exit(EXIT_FAILURE); 474 } 475 } else { 476 /* default input file is stdin */ 477 #ifdef USE_SETMODE /* need to hack file mode? */ 478 setmode(fileno(stdin), O_BINARY); 479 #endif 480 #ifdef USE_FDOPEN /* need to re-open in binary mode? */ 481 if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) { 482 fprintf(stderr, "%s: can't open stdin\n", progname); 483 exit(EXIT_FAILURE); 484 } 485 #else 486 infile = stdin; 487 #endif 488 } 489 490 /* Scan the JPEG headers. */ 491 (void) scan_JPEG_header(verbose); 492 493 /* All done. */ 494 exit(EXIT_SUCCESS); 495 return 0; /* suppress no-return-value warnings */ 496 } 497
