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Extensive hack to pre-read the YCbCr sampling information from the jpeg

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This commit is contained in:
Frank Warmerdam 2002-07-31 20:56:15 +00:00
parent afb8476510
commit fe7352c450
1 changed files with 86 additions and 2 deletions
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88
libtiff/tif_jpeg.c
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@ -1,4 +1,4 @@
/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/tif_jpeg.c,v 1.8 2002-03-06 14:07:27 warmerda Exp $ */
/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/tif_jpeg.c,v 1.9 2002-07-31 20:56:15 warmerda Exp $ */
/*
* Copyright (c) 1994-1997 Sam Leffler
@ -42,6 +42,9 @@
#include <stdio.h>
#include <setjmp.h>
int TIFFFillStrip(TIFF*, tstrip_t);
int TIFFFillTile(TIFF*, ttile_t);
/* We undefine FAR to avoid conflict with JPEG definition */
#ifdef FAR
@ -116,6 +119,8 @@ typedef struct {
int jpegquality; /* Compression quality level */
int jpegcolormode; /* Auto RGB<=>YCbCr convert? */
int jpegtablesmode; /* What to put in JPEGTables */
int ycbcrsampling_fetched;
} JPEGState;
#define JState(tif) ((JPEGState*)(tif)->tif_data)
@ -681,7 +686,7 @@ JPEGPreDecode(TIFF* tif, tsample_t s)
sp->cinfo.d.comp_info[0].v_samp_factor != sp->v_sampling) {
TIFFWarning(module,
"Improper JPEG sampling factors %d,%d\n"
"Apparently should be %d,%d,"
"Apparently should be %d,%d, "
"decompressor will try reading with "
"sampling %d,%d",
sp->cinfo.d.comp_info[0].h_samp_factor,
@ -1359,6 +1364,73 @@ JPEGVSetField(TIFF* tif, ttag_t tag, va_list ap)
return (1);
}
/*
* Some JPEG-in-TIFF produces do not emit the YCBCRSUBSAMPLING values in
* the TIFF tags, but still use non-default (2,2) values within the jpeg
* data stream itself. In order for TIFF applications to work properly
* - for instance to get the strip buffer size right - it is imperative
* that the subsampling be available before we start reading the image
* data normally. This function will attempt to load the first strip in
* order to get the sampling values from the jpeg data stream. Various
* hacks are various places are done to ensure this function gets called
* before the td_ycbcrsubsampling values are used from the directory structure,
* including calling TIFFGetField() for the YCBCRSUBSAMPLING field from
* TIFFStripSize(), and the printing code in tif_print.c.
*
* Note that JPEGPreDeocode() will produce a fairly loud warning when the
* discovered sampling does not match the default sampling (2,2) or whatever
* was actually in the tiff tags.
*
* Problems:
* o This code will cause one whole strip/tile of compressed data to be
* loaded just to get the tags right, even if the imagery is never read.
* It would be more efficient to just load a bit of the header, and
* initialize things from that.
* o This code doesn't know whether or not the tag actually did occur in
* the file. If it knew this it could skip the hack but this is hard to
* know since we have already set the "field set" bit for the subsampling
* TIFFInitJPEG().
*
* See the bug in bugzilla for details:
*
* http://bugzilla.remotesensing.org/show_bug.cgi?id=168
*
* Frank Warmerdam, July 2002
*/
static void
JPEGFixupTestSubsampling( TIFF * tif )
{
#if CHECK_JPEG_YCBCR_SUBSAMPLING == 1
JPEGState *sp = JState(tif);
/*
* Some JPEG-in-TIFF files don't provide the ycbcrsampling tags,
* and use a sampling schema other than the default 2,2. To handle
* this we actually have to scan the header of a strip or tile of
* jpeg data to get the sampling.
*/
if( !sp->cinfo.comm.is_decompressor
|| sp->ycbcrsampling_fetched )
return;
sp->ycbcrsampling_fetched = 1;
if( TIFFIsTiled( tif ) )
{
if( !TIFFFillTile( tif, 0 ) )
return;
}
else
{
if( !TIFFFillStrip( tif, 0 ) )
return;
}
TIFFSetField( tif, TIFFTAG_YCBCRSUBSAMPLING,
(uint16) sp->h_sampling, (uint16) sp->v_sampling );
#endif /* CHECK_JPEG_YCBCR_SUBSAMPLING == 1 */
}
static int
JPEGVGetField(TIFF* tif, ttag_t tag, va_list ap)
{
@ -1380,6 +1452,10 @@ JPEGVGetField(TIFF* tif, ttag_t tag, va_list ap)
case TIFFTAG_JPEGTABLESMODE:
*va_arg(ap, int*) = sp->jpegtablesmode;
break;
case TIFFTAG_YCBCRSUBSAMPLING:
JPEGFixupTestSubsampling( tif );
return (*sp->vgetparent)(tif, tag, ap);
break;
default:
return (*sp->vgetparent)(tif, tag, ap);
}
@ -1456,6 +1532,8 @@ TIFFInitJPEG(TIFF* tif, int scheme)
sp->jpegcolormode = JPEGCOLORMODE_RAW;
sp->jpegtablesmode = JPEGTABLESMODE_QUANT | JPEGTABLESMODE_HUFF;
sp->ycbcrsampling_fetched = 0;
/*
* Install codec methods.
*/
@ -1483,6 +1561,12 @@ TIFFInitJPEG(TIFF* tif, int scheme)
if (tif->tif_mode == O_RDONLY) {
if (!TIFFjpeg_create_decompress(sp))
return (0);
/*
* Mark the TIFFTAG_YCBCRSAMPLES as present even if it is not
* see: JPEGFixupTestSubsampling().
*/
TIFFSetFieldBit( tif, FIELD_YCBCRSUBSAMPLING );
} else {
if (!TIFFjpeg_create_compress(sp))
return (0);