ref: f35d5ee5b036b7b4fa59b1839f52fca15b7f99f9
dir: /sys/src/cmd/gs/jpeg/rdjpgcom.c/
/* * 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 */ }