1
by Bill Allombert
Import upstream version 6b |
1 |
/*
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2 |
* rdjpgcom.c
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*
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* Copyright (C) 1994-1997, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains a very simple stand-alone application that displays
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* the text in COM (comment) markers in a JFIF file.
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* This may be useful as an example of the minimum logic needed to parse
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* JPEG markers.
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*/
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#define JPEG_CJPEG_DJPEG /* to get the command-line config symbols */ |
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#include "jinclude.h" /* get auto-config symbols, <stdio.h> */ |
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#include <ctype.h> /* to declare isupper(), tolower() */ |
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#ifdef USE_SETMODE
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#include <fcntl.h> /* to declare setmode()'s parameter macros */ |
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/* If you have setmode() but not <io.h>, just delete this line: */
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#include <io.h> /* to declare setmode() */ |
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#endif
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#ifdef USE_CCOMMAND /* command-line reader for Macintosh */ |
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#ifdef __MWERKS__
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#include <SIOUX.h> /* Metrowerks needs this */ |
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#include <console.h> /* ... and this */ |
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#endif
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#ifdef THINK_C
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#include <console.h> /* Think declares it here */ |
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#endif
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#endif
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#ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */ |
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#define READ_BINARY "r"
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#else
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#ifdef VMS /* VMS is very nonstandard */ |
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#define READ_BINARY "rb", "ctx=stm"
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#else /* standard ANSI-compliant case */ |
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#define READ_BINARY "rb"
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#endif
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#endif
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#ifndef EXIT_FAILURE /* define exit() codes if not provided */ |
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#define EXIT_FAILURE 1
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#endif
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#ifndef EXIT_SUCCESS
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#ifdef VMS
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#define EXIT_SUCCESS 1 /* VMS is very nonstandard */ |
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#else
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#define EXIT_SUCCESS 0
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#endif
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#endif
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/*
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* These macros are used to read the input file.
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* To reuse this code in another application, you might need to change these.
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*/
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static FILE * infile; /* input JPEG file */ |
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/* Return next input byte, or EOF if no more */
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#define NEXTBYTE() getc(infile)
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/* Error exit handler */
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#define ERREXIT(msg) (fprintf(stderr, "%s\n", msg), exit(EXIT_FAILURE))
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/* Read one byte, testing for EOF */
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static int |
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read_1_byte (void) |
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{
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int c; |
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c = NEXTBYTE(); |
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if (c == EOF) |
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ERREXIT("Premature EOF in JPEG file"); |
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return c; |
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}
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/* Read 2 bytes, convert to unsigned int */
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/* All 2-byte quantities in JPEG markers are MSB first */
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static unsigned int |
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read_2_bytes (void) |
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{
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int c1, c2; |
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c1 = NEXTBYTE(); |
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if (c1 == EOF) |
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ERREXIT("Premature EOF in JPEG file"); |
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c2 = NEXTBYTE(); |
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if (c2 == EOF) |
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ERREXIT("Premature EOF in JPEG file"); |
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return (((unsigned int) c1) << 8) + ((unsigned int) c2); |
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}
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/*
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* JPEG markers consist of one or more 0xFF bytes, followed by a marker
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* code byte (which is not an FF). Here are the marker codes of interest
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* in this program. (See jdmarker.c for a more complete list.)
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*/
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#define M_SOF0 0xC0 /* Start Of Frame N */ |
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#define M_SOF1 0xC1 /* N indicates which compression process */ |
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#define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */ |
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#define M_SOF3 0xC3
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#define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */ |
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#define M_SOF6 0xC6
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#define M_SOF7 0xC7
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#define M_SOF9 0xC9
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#define M_SOF10 0xCA
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#define M_SOF11 0xCB
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#define M_SOF13 0xCD
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#define M_SOF14 0xCE
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#define M_SOF15 0xCF
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#define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */ |
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#define M_EOI 0xD9 /* End Of Image (end of datastream) */ |
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#define M_SOS 0xDA /* Start Of Scan (begins compressed data) */ |
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#define M_APP0 0xE0 /* Application-specific marker, type N */ |
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#define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */ |
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#define M_COM 0xFE /* COMment */ |
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/*
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* Find the next JPEG marker and return its marker code.
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* We expect at least one FF byte, possibly more if the compressor used FFs
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* to pad the file.
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* There could also be non-FF garbage between markers. The treatment of such
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* garbage is unspecified; we choose to skip over it but emit a warning msg.
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* NB: this routine must not be used after seeing SOS marker, since it will
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* not deal correctly with FF/00 sequences in the compressed image data...
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*/
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static int |
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next_marker (void) |
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{
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int c; |
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int discarded_bytes = 0; |
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/* Find 0xFF byte; count and skip any non-FFs. */
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c = read_1_byte(); |
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while (c != 0xFF) { |
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discarded_bytes++; |
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c = read_1_byte(); |
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}
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/* Get marker code byte, swallowing any duplicate FF bytes. Extra FFs
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* are legal as pad bytes, so don't count them in discarded_bytes.
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*/
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do { |
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c = read_1_byte(); |
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} while (c == 0xFF); |
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if (discarded_bytes != 0) { |
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fprintf(stderr, "Warning: garbage data found in JPEG file\n"); |
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}
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return c; |
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}
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/*
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* Read the initial marker, which should be SOI.
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* For a JFIF file, the first two bytes of the file should be literally
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* 0xFF M_SOI. To be more general, we could use next_marker, but if the
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* input file weren't actually JPEG at all, next_marker might read the whole
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* file and then return a misleading error message...
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*/
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static int |
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first_marker (void) |
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{
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int c1, c2; |
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c1 = NEXTBYTE(); |
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c2 = NEXTBYTE(); |
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if (c1 != 0xFF || c2 != M_SOI) |
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ERREXIT("Not a JPEG file"); |
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return c2; |
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}
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/*
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* Most types of marker are followed by a variable-length parameter segment.
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* This routine skips over the parameters for any marker we don't otherwise
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* want to process.
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* Note that we MUST skip the parameter segment explicitly in order not to
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* be fooled by 0xFF bytes that might appear within the parameter segment;
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* such bytes do NOT introduce new markers.
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*/
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static void |
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skip_variable (void) |
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/* Skip over an unknown or uninteresting variable-length marker */
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{
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unsigned int length; |
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/* Get the marker parameter length count */
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length = read_2_bytes(); |
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/* Length includes itself, so must be at least 2 */
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if (length < 2) |
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ERREXIT("Erroneous JPEG marker length"); |
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length -= 2; |
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/* Skip over the remaining bytes */
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while (length > 0) { |
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(void) read_1_byte(); |
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length--; |
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}
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}
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/*
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* Process a COM marker.
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* We want to print out the marker contents as legible text;
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* we must guard against non-text junk and varying newline representations.
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*/
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static void |
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process_COM (void) |
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{
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unsigned int length; |
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int ch; |
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int lastch = 0; |
|
4.1.4
by Bill Allombert
* New upstream release |
226 |
|
1
by Bill Allombert
Import upstream version 6b |
227 |
/* Get the marker parameter length count */
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length = read_2_bytes(); |
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/* Length includes itself, so must be at least 2 */
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if (length < 2) |
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ERREXIT("Erroneous JPEG marker length"); |
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length -= 2; |
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while (length > 0) { |
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ch = read_1_byte(); |
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/* Emit the character in a readable form.
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* Nonprintables are converted to \nnn form,
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* while \ is converted to \\.
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* Newlines in CR, CR/LF, or LF form will be printed as one newline.
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*/
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if (ch == '\r') { |
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printf("\n"); |
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} else if (ch == '\n') { |
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if (lastch != '\r') |
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printf("\n"); |
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} else if (ch == '\\') { |
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printf("\\\\"); |
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} else if (isprint(ch)) { |
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putc(ch, stdout); |
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} else { |
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printf("\\%03o", ch); |
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}
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lastch = ch; |
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length--; |
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}
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printf("\n"); |
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}
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/*
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* Process a SOFn marker.
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* This code is only needed if you want to know the image dimensions...
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*/
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static void |
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process_SOFn (int marker) |
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{
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unsigned int length; |
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unsigned int image_height, image_width; |
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int data_precision, num_components; |
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const char * process; |
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int ci; |
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273 |
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length = read_2_bytes(); /* usual parameter length count */ |
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276 |
data_precision = read_1_byte(); |
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image_height = read_2_bytes(); |
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image_width = read_2_bytes(); |
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num_components = read_1_byte(); |
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280 |
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switch (marker) { |
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case M_SOF0: process = "Baseline"; break; |
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case M_SOF1: process = "Extended sequential"; break; |
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case M_SOF2: process = "Progressive"; break; |
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case M_SOF3: process = "Lossless"; break; |
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case M_SOF5: process = "Differential sequential"; break; |
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case M_SOF6: process = "Differential progressive"; break; |
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case M_SOF7: process = "Differential lossless"; break; |
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case M_SOF9: process = "Extended sequential, arithmetic coding"; break; |
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case M_SOF10: process = "Progressive, arithmetic coding"; break; |
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case M_SOF11: process = "Lossless, arithmetic coding"; break; |
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case M_SOF13: process = "Differential sequential, arithmetic coding"; break; |
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case M_SOF14: process = "Differential progressive, arithmetic coding"; break; |
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case M_SOF15: process = "Differential lossless, arithmetic coding"; break; |
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default: process = "Unknown"; break; |
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296 |
}
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297 |
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298 |
printf("JPEG image is %uw * %uh, %d color components, %d bits per sample\n", |
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image_width, image_height, num_components, data_precision); |
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printf("JPEG process: %s\n", process); |
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301 |
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302 |
if (length != (unsigned int) (8 + num_components * 3)) |
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ERREXIT("Bogus SOF marker length"); |
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304 |
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305 |
for (ci = 0; ci < num_components; ci++) { |
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306 |
(void) read_1_byte(); /* Component ID code */ |
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307 |
(void) read_1_byte(); /* H, V sampling factors */ |
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308 |
(void) read_1_byte(); /* Quantization table number */ |
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309 |
}
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310 |
}
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311 |
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/*
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314 |
* Parse the marker stream until SOS or EOI is seen;
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315 |
* display any COM markers.
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316 |
* While the companion program wrjpgcom will always insert COM markers before
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317 |
* SOFn, other implementations might not, so we scan to SOS before stopping.
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* If we were only interested in the image dimensions, we would stop at SOFn.
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319 |
* (Conversely, if we only cared about COM markers, there would be no need
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320 |
* for special code to handle SOFn; we could treat it like other markers.)
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321 |
*/
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322 |
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323 |
static int |
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324 |
scan_JPEG_header (int verbose) |
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325 |
{
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326 |
int marker; |
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327 |
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328 |
/* Expect SOI at start of file */
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329 |
if (first_marker() != M_SOI) |
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330 |
ERREXIT("Expected SOI marker first"); |
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331 |
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332 |
/* Scan miscellaneous markers until we reach SOS. */
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333 |
for (;;) { |
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334 |
marker = next_marker(); |
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335 |
switch (marker) { |
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336 |
/* Note that marker codes 0xC4, 0xC8, 0xCC are not, and must not be,
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337 |
* treated as SOFn. C4 in particular is actually DHT.
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338 |
*/
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339 |
case M_SOF0: /* Baseline */ |
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340 |
case M_SOF1: /* Extended sequential, Huffman */ |
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341 |
case M_SOF2: /* Progressive, Huffman */ |
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342 |
case M_SOF3: /* Lossless, Huffman */ |
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343 |
case M_SOF5: /* Differential sequential, Huffman */ |
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344 |
case M_SOF6: /* Differential progressive, Huffman */ |
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345 |
case M_SOF7: /* Differential lossless, Huffman */ |
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346 |
case M_SOF9: /* Extended sequential, arithmetic */ |
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347 |
case M_SOF10: /* Progressive, arithmetic */ |
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348 |
case M_SOF11: /* Lossless, arithmetic */ |
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349 |
case M_SOF13: /* Differential sequential, arithmetic */ |
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350 |
case M_SOF14: /* Differential progressive, arithmetic */ |
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351 |
case M_SOF15: /* Differential lossless, arithmetic */ |
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352 |
if (verbose) |
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353 |
process_SOFn(marker); |
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354 |
else
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355 |
skip_variable(); |
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356 |
break; |
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357 |
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358 |
case M_SOS: /* stop before hitting compressed data */ |
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359 |
return marker; |
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360 |
||
361 |
case M_EOI: /* in case it's a tables-only JPEG stream */ |
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362 |
return marker; |
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363 |
||
364 |
case M_COM: |
|
365 |
process_COM(); |
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366 |
break; |
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367 |
||
368 |
case M_APP12: |
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369 |
/* Some digital camera makers put useful textual information into
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370 |
* APP12 markers, so we print those out too when in -verbose mode.
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371 |
*/
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372 |
if (verbose) { |
|
373 |
printf("APP12 contains:\n"); |
|
374 |
process_COM(); |
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375 |
} else |
|
376 |
skip_variable(); |
|
377 |
break; |
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378 |
||
379 |
default: /* Anything else just gets skipped */ |
|
380 |
skip_variable(); /* we assume it has a parameter count... */ |
|
381 |
break; |
|
382 |
}
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383 |
} /* end loop */ |
|
384 |
}
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385 |
||
386 |
||
387 |
/* Command line parsing code */
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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 |
{
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|
396 |
fprintf(stderr, "rdjpgcom displays any textual comments in a JPEG file.\n"); |
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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 |
}
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405 |
||
406 |
||
407 |
static int |
|
408 |
keymatch (char * arg, const char * keyword, int minchars) |
|
409 |
/* Case-insensitive matching of (possibly abbreviated) keyword switches. */
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|
410 |
/* keyword is the constant keyword (must be lower case already), */
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|
411 |
/* minchars is length of minimum legal abbreviation. */
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|
412 |
{
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|
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 |
}
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|
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 |
/*
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|
433 |
* The main program.
|
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434 |
*/
|
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435 |
||
436 |
int
|
|
437 |
main (int argc, char **argv) |
|
438 |
{
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|
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 |
}
|