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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: 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
scan_JPEG_header(int verbose,int raw)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
usage(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
keymatch(char * arg,const char * keyword,int minchars)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
main(int argc,char ** argv)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