--- /dev/null
+/*
+ * rdjpgcom.c
+ *
+ * Copyright (C) 1994-1997, Thomas G. Lane.
+ * This file is part of the Independent JPEG Group's software.
+ * For conditions of distribution and use, see the accompanying README file.
+ *
+ * This file contains a very simple stand-alone application that displays
+ * the text in COM (comment) markers in a JFIF file.
+ * This may be useful as an example of the minimum logic needed to parse
+ * JPEG markers.
+ */
+
+#define JPEG_CJPEG_DJPEG /* to get the command-line config symbols */
+#include "jinclude.h" /* get auto-config symbols, <stdio.h> */
+
+#include <ctype.h> /* to declare isupper(), tolower() */
+#ifdef USE_SETMODE
+#include <fcntl.h> /* to declare setmode()'s parameter macros */
+/* If you have setmode() but not <io.h>, just delete this line: */
+#include <io.h> /* to declare setmode() */
+#endif
+
+#ifdef USE_CCOMMAND /* command-line reader for Macintosh */
+#ifdef __MWERKS__
+#include <SIOUX.h> /* Metrowerks needs this */
+#include <console.h> /* ... and this */
+#endif
+#ifdef THINK_C
+#include <console.h> /* Think declares it here */
+#endif
+#endif
+
+#ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */
+#define READ_BINARY "r"
+#else
+#ifdef VMS /* VMS is very nonstandard */
+#define READ_BINARY "rb", "ctx=stm"
+#else /* standard ANSI-compliant case */
+#define READ_BINARY "rb"
+#endif
+#endif
+
+#ifndef EXIT_FAILURE /* define exit() codes if not provided */
+#define EXIT_FAILURE 1
+#endif
+#ifndef EXIT_SUCCESS
+#ifdef VMS
+#define EXIT_SUCCESS 1 /* VMS is very nonstandard */
+#else
+#define EXIT_SUCCESS 0
+#endif
+#endif
+
+
+/*
+ * These macros are used to read the input file.
+ * To reuse this code in another application, you might need to change these.
+ */
+
+static FILE * infile; /* input JPEG file */
+
+/* Return next input byte, or EOF if no more */
+#define NEXTBYTE() getc(infile)
+
+
+/* Error exit handler */
+#define ERREXIT(msg) (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE))
+
+
+/* Read one byte, testing for EOF */
+static int
+read_1_byte (void)
+{
+ int c;
+
+ c = NEXTBYTE();
+ if (c == EOF)
+ ERREXIT("Premature EOF in JPEG file");
+ return c;
+}
+
+/* Read 2 bytes, convert to unsigned int */
+/* All 2-byte quantities in JPEG markers are MSB first */
+static unsigned int
+read_2_bytes (void)
+{
+ int c1, c2;
+
+ c1 = NEXTBYTE();
+ if (c1 == EOF)
+ ERREXIT("Premature EOF in JPEG file");
+ c2 = NEXTBYTE();
+ if (c2 == EOF)
+ ERREXIT("Premature EOF in JPEG file");
+ return (((unsigned int) c1) << 8) + ((unsigned int) c2);
+}
+
+
+/*
+ * JPEG markers consist of one or more 0xFF bytes, followed by a marker
+ * code byte (which is not an FF). Here are the marker codes of interest
+ * in this program. (See jdmarker.c for a more complete list.)
+ */
+
+#define M_SOF0 0xC0 /* Start Of Frame N */
+#define M_SOF1 0xC1 /* N indicates which compression process */
+#define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */
+#define M_SOF3 0xC3
+#define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */
+#define M_SOF6 0xC6
+#define M_SOF7 0xC7
+#define M_SOF9 0xC9
+#define M_SOF10 0xCA
+#define M_SOF11 0xCB
+#define M_SOF13 0xCD
+#define M_SOF14 0xCE
+#define M_SOF15 0xCF
+#define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */
+#define M_EOI 0xD9 /* End Of Image (end of datastream) */
+#define M_SOS 0xDA /* Start Of Scan (begins compressed data) */
+#define M_APP0 0xE0 /* Application-specific marker, type N */
+#define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */
+#define M_COM 0xFE /* COMment */
+
+
+/*
+ * Find the next JPEG marker and return its marker code.
+ * We expect at least one FF byte, possibly more if the compressor used FFs
+ * to pad the file.
+ * There could also be non-FF garbage between markers. The treatment of such
+ * garbage is unspecified; we choose to skip over it but emit a warning msg.
+ * NB: this routine must not be used after seeing SOS marker, since it will
+ * not deal correctly with FF/00 sequences in the compressed image data...
+ */
+
+static int
+next_marker (void)
+{
+ int c;
+ int discarded_bytes = 0;
+
+ /* Find 0xFF byte; count and skip any non-FFs. */
+ c = read_1_byte();
+ while (c != 0xFF) {
+ discarded_bytes++;
+ c = read_1_byte();
+ }
+ /* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs
+ * are legal as pad bytes, so don't count them in discarded_bytes.
+ */
+ do {
+ c = read_1_byte();
+ } while (c == 0xFF);
+
+ if (discarded_bytes != 0) {
+ fprintf(stderr, "Warning: garbage data found in JPEG file\n");
+ }
+
+ return c;
+}
+
+
+/*
+ * Read the initial marker, which should be SOI.
+ * For a JFIF file, the first two bytes of the file should be literally
+ * 0xFF M_SOI. To be more general, we could use next_marker, but if the
+ * input file weren't actually JPEG at all, next_marker might read the whole
+ * file and then return a misleading error message...
+ */
+
+static int
+first_marker (void)
+{
+ int c1, c2;
+
+ c1 = NEXTBYTE();
+ c2 = NEXTBYTE();
+ if (c1 != 0xFF || c2 != M_SOI)
+ ERREXIT("Not a JPEG file");
+ return c2;
+}
+
+
+/*
+ * Most types of marker are followed by a variable-length parameter segment.
+ * This routine skips over the parameters for any marker we don't otherwise
+ * want to process.
+ * Note that we MUST skip the parameter segment explicitly in order not to
+ * be fooled by 0xFF bytes that might appear within the parameter segment;
+ * such bytes do NOT introduce new markers.
+ */
+
+static void
+skip_variable (void)
+/* Skip over an unknown or uninteresting variable-length marker */
+{
+ unsigned int length;
+
+ /* Get the marker parameter length count */
+ length = read_2_bytes();
+ /* Length includes itself, so must be at least 2 */
+ if (length < 2)
+ ERREXIT("Erroneous JPEG marker length");
+ length -= 2;
+ /* Skip over the remaining bytes */
+ while (length > 0) {
+ (void) read_1_byte();
+ length--;
+ }
+}
+
+
+/*
+ * Process a COM marker.
+ * We want to print out the marker contents as legible text;
+ * we must guard against non-text junk and varying newline representations.
+ */
+
+static void
+process_COM (void)
+{
+ unsigned int length;
+ int ch;
+ int lastch = 0;
+
+ /* Get the marker parameter length count */
+ length = read_2_bytes();
+ /* Length includes itself, so must be at least 2 */
+ if (length < 2)
+ ERREXIT("Erroneous JPEG marker length");
+ length -= 2;
+
+ while (length > 0) {
+ ch = read_1_byte();
+ /* Emit the character in a readable form.
+ * Nonprintables are converted to \nnn form,
+ * while \ is converted to \\.
+ * Newlines in CR, CR/LF, or LF form will be printed as one newline.
+ */
+ if (ch == '\r') {
+ printf("\n");
+ } else if (ch == '\n') {
+ if (lastch != '\r')
+ printf("\n");
+ } else if (ch == '\\') {
+ printf("\\\\");
+ } else if (isprint(ch)) {
+ putc(ch, stdout);
+ } else {
+ printf("\\%03o", ch);
+ }
+ lastch = ch;
+ length--;
+ }
+ printf("\n");
+}
+
+
+/*
+ * Process a SOFn marker.
+ * This code is only needed if you want to know the image dimensions...
+ */
+
+static void
+process_SOFn (int marker)
+{
+ unsigned int length;
+ unsigned int image_height, image_width;
+ int data_precision, num_components;
+ const char * process;
+ int ci;
+
+ length = read_2_bytes(); /* usual parameter length count */
+
+ data_precision = read_1_byte();
+ image_height = read_2_bytes();
+ image_width = read_2_bytes();
+ num_components = read_1_byte();
+
+ switch (marker) {
+ case M_SOF0: process = "Baseline"; break;
+ case M_SOF1: process = "Extended sequential"; break;
+ case M_SOF2: process = "Progressive"; break;
+ case M_SOF3: process = "Lossless"; break;
+ case M_SOF5: process = "Differential sequential"; break;
+ case M_SOF6: process = "Differential progressive"; break;
+ case M_SOF7: process = "Differential lossless"; break;
+ case M_SOF9: process = "Extended sequential, arithmetic coding"; break;
+ case M_SOF10: process = "Progressive, arithmetic coding"; break;
+ case M_SOF11: process = "Lossless, arithmetic coding"; break;
+ case M_SOF13: process = "Differential sequential, arithmetic coding"; break;
+ case M_SOF14: process = "Differential progressive, arithmetic coding"; break;
+ case M_SOF15: process = "Differential lossless, arithmetic coding"; break;
+ default: process = "Unknown"; break;
+ }
+
+ printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n",
+ image_width, image_height, num_components, data_precision);
+ printf("JPEG process: %s\n", process);
+
+ if (length != (unsigned int) (8 + num_components * 3))
+ ERREXIT("Bogus SOF marker length");
+
+ for (ci = 0; ci < num_components; ci++) {
+ (void) read_1_byte(); /* Component ID code */
+ (void) read_1_byte(); /* H, V sampling factors */
+ (void) read_1_byte(); /* Quantization table number */
+ }
+}
+
+
+/*
+ * Parse the marker stream until SOS or EOI is seen;
+ * display any COM markers.
+ * While the companion program wrjpgcom will always insert COM markers before
+ * SOFn, other implementations might not, so we scan to SOS before stopping.
+ * If we were only interested in the image dimensions, we would stop at SOFn.
+ * (Conversely, if we only cared about COM markers, there would be no need
+ * for special code to handle SOFn; we could treat it like other markers.)
+ */
+
+static int
+scan_JPEG_header (int verbose)
+{
+ int marker;
+
+ /* Expect SOI at start of file */
+ if (first_marker() != M_SOI)
+ ERREXIT("Expected SOI marker first");
+
+ /* Scan miscellaneous markers until we reach SOS. */
+ for (;;) {
+ marker = next_marker();
+ switch (marker) {
+ /* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be,
+ * treated as SOFn. C4 in particular is actually DHT.
+ */
+ case M_SOF0: /* Baseline */
+ case M_SOF1: /* Extended sequential, Huffman */
+ case M_SOF2: /* Progressive, Huffman */
+ case M_SOF3: /* Lossless, Huffman */
+ case M_SOF5: /* Differential sequential, Huffman */
+ case M_SOF6: /* Differential progressive, Huffman */
+ case M_SOF7: /* Differential lossless, Huffman */
+ case M_SOF9: /* Extended sequential, arithmetic */
+ case M_SOF10: /* Progressive, arithmetic */
+ case M_SOF11: /* Lossless, arithmetic */
+ case M_SOF13: /* Differential sequential, arithmetic */
+ case M_SOF14: /* Differential progressive, arithmetic */
+ case M_SOF15: /* Differential lossless, arithmetic */
+ if (verbose)
+ process_SOFn(marker);
+ else
+ skip_variable();
+ break;
+
+ case M_SOS: /* stop before hitting compressed data */
+ return marker;
+
+ case M_EOI: /* in case it's a tables-only JPEG stream */
+ return marker;
+
+ case M_COM:
+ process_COM();
+ break;
+
+ case M_APP12:
+ /* Some digital camera makers put useful textual information into
+ * APP12 markers, so we print those out too when in -verbose mode.
+ */
+ if (verbose) {
+ printf("APP12 contains:\n");
+ process_COM();
+ } else
+ skip_variable();
+ break;
+
+ default: /* Anything else just gets skipped */
+ skip_variable(); /* we assume it has a parameter count... */
+ break;
+ }
+ } /* end loop */
+}
+
+
+/* Command line parsing code */
+
+static const char * progname; /* program name for error messages */
+
+
+static void
+usage (void)
+/* complain about bad command line */
+{
+ fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n");
+
+ fprintf(stderr, "Usage: %s [switches] [inputfile]\n", progname);
+
+ fprintf(stderr, "Switches (names may be abbreviated):\n");
+ fprintf(stderr, " -verbose Also display dimensions of JPEG image\n");
+
+ exit(EXIT_FAILURE);
+}
+
+
+static int
+keymatch (char * arg, const char * keyword, int minchars)
+/* Case-insensitive matching of (possibly abbreviated) keyword switches. */
+/* keyword is the constant keyword (must be lower case already), */
+/* minchars is length of minimum legal abbreviation. */
+{
+ register int ca, ck;
+ register int nmatched = 0;
+
+ while ((ca = *arg++) != '\0') {
+ if ((ck = *keyword++) == '\0')
+ return 0; /* arg longer than keyword, no good */
+ if (isupper(ca)) /* force arg to lcase (assume ck is already) */
+ ca = tolower(ca);
+ if (ca != ck)
+ return 0; /* no good */
+ nmatched++; /* count matched characters */
+ }
+ /* reached end of argument; fail if it's too short for unique abbrev */
+ if (nmatched < minchars)
+ return 0;
+ return 1; /* A-OK */
+}
+
+
+/*
+ * The main program.
+ */
+
+int
+main (int argc, char **argv)
+{
+ int argn;
+ char * arg;
+ int verbose = 0;
+
+ /* On Mac, fetch a command line. */
+#ifdef USE_CCOMMAND
+ argc = ccommand(&argv);
+#endif
+
+ progname = argv[0];
+ if (progname == NULL || progname[0] == 0)
+ progname = "rdjpgcom"; /* in case C library doesn't provide it */
+
+ /* Parse switches, if any */
+ for (argn = 1; argn < argc; argn++) {
+ arg = argv[argn];
+ if (arg[0] != '-')
+ break; /* not switch, must be file name */
+ arg++; /* advance over '-' */
+ if (keymatch(arg, "verbose", 1)) {
+ verbose++;
+ } else
+ usage();
+ }
+
+ /* Open the input file. */
+ /* Unix style: expect zero or one file name */
+ if (argn < argc-1) {
+ fprintf(stderr, "%s: only one input file\n", progname);
+ usage();
+ }
+ if (argn < argc) {
+ if ((infile = fopen(argv[argn], READ_BINARY)) == NULL) {
+ fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
+ exit(EXIT_FAILURE);
+ }
+ } else {
+ /* default input file is stdin */
+#ifdef USE_SETMODE /* need to hack file mode? */
+ setmode(fileno(stdin), O_BINARY);
+#endif
+#ifdef USE_FDOPEN /* need to re-open in binary mode? */
+ if ((infile = fdopen(fileno(stdin), READ_BINARY)) == NULL) {
+ fprintf(stderr, "%s: can't open stdin\n", progname);
+ exit(EXIT_FAILURE);
+ }
+#else
+ infile = stdin;
+#endif
+ }
+
+ /* Scan the JPEG headers. */
+ (void) scan_JPEG_header(verbose);
+
+ /* All done. */
+ exit(EXIT_SUCCESS);
+ return 0; /* suppress no-return-value warnings */
+}
projects / synfig.git / blobdiff