core/libs/jpeg-6b/rdjpgcom.c

   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 }