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rdjpgcom.c
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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
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
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
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
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
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
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();
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
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 
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]);
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);
484  }
485 #else
486  infile = stdin;
487 #endif
488  }
489 
490  /* Scan the JPEG headers. */
492 
493  /* All done. */
495  return 0; /* suppress no-return-value warnings */
496 }
int process()
#define fopen
Definition: xxstdio.h:21
int printf()
static void
Definition: fpif.c:118
#define c(n)
Definition: gpos-common.c:150
#define putc
Definition: jbib.h:20
int image_height
int image_width
#define ERREXIT(msg)
Definition: rdjpgcom.c:68
static void process_COM(void)
Definition: rdjpgcom.c:221
#define M_SOF7
Definition: rdjpgcom.c:112
int main(int argc, char **argv)
Definition: rdjpgcom.c:437
#define M_SOF6
Definition: rdjpgcom.c:111
#define M_EOI
Definition: rdjpgcom.c:120
#define M_SOF11
Definition: rdjpgcom.c:115
#define M_SOF9
Definition: rdjpgcom.c:113
static void skip_variable(void)
Definition: rdjpgcom.c:195
#define EXIT_SUCCESS
Definition: rdjpgcom.c:51
#define M_SOF15
Definition: rdjpgcom.c:118
#define READ_BINARY
Definition: rdjpgcom.c:40
#define EXIT_FAILURE
Definition: rdjpgcom.c:45
#define NEXTBYTE()
Definition: rdjpgcom.c:64
static void process_SOFn(int marker)
Definition: rdjpgcom.c:266
#define M_SOF3
Definition: rdjpgcom.c:109
#define M_SOF13
Definition: rdjpgcom.c:116
#define M_APP12
Definition: rdjpgcom.c:123
static unsigned int read_2_bytes(void)
Definition: rdjpgcom.c:86
static int scan_JPEG_header(int verbose)
Definition: rdjpgcom.c:324
#define M_SOF10
Definition: rdjpgcom.c:114
#define M_SOF1
Definition: rdjpgcom.c:107
static int keymatch(char *arg, const char *keyword, int minchars)
Definition: rdjpgcom.c:408
#define M_SOI
Definition: rdjpgcom.c:119
#define M_SOF5
Definition: rdjpgcom.c:110
static const char * progname
Definition: rdjpgcom.c:389
static void usage(void)
Definition: rdjpgcom.c:393
static int read_1_byte(void)
Definition: rdjpgcom.c:73
#define M_SOF14
Definition: rdjpgcom.c:117
#define M_SOF0
Definition: rdjpgcom.c:106
static int first_marker(void)
Definition: rdjpgcom.c:173
static int next_marker(void)
Definition: rdjpgcom.c:138
#define M_COM
Definition: rdjpgcom.c:124
#define M_SOF2
Definition: rdjpgcom.c:108
static FILE * infile
Definition: rdjpgcom.c:61
#define M_SOS
Definition: rdjpgcom.c:121
#define NULL
Definition: ftobjs.h:61
void exit()
#define EOF
Definition: afmparse.c:59
#define O_BINARY
Definition: config.h:393
#define fileno
Definition: win32lib.h:72
#define fprintf
Definition: mendex.h:64
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int setmode()
#define tolower(ch)
Definition: utype.h:137
#define isupper(ch)
Definition: utype.h:80
static int lastch
Definition: macbinary.c:1066
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#define c2
Definition: t1io.c:53
#define c1
Definition: t1io.c:52
def_key keyword[6]
Definition: t1part.c:256
#define FILE
Definition: t1stdio.h:34
ch
Definition: t4ht.c:1443
return() int(((double) *(font_tbl[cur_fnt].wtbl+(int)(*(font_tbl[cur_fnt].char_wi+(int)(ch - font_tbl[cur_fnt].char_f)% 256)))/(double)(1L<< 20)) *(double) font_tbl[cur_fnt].scale)
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Definition: jpeg.c:35
#define argv
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#define argc
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