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April 2012
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2012.04.27 15:35 "Re: YCbCr/JPEG issue in 4.0.1", by Charles Auer
The following tags are found in quad-jpeg.tif (AsTiffTagViewer 2.00, Aware Systems):ImageWidth (1 Short): 512ImageLength (1 Short): 384BitsPerSample (3 Short): 8, 8, 8Compression (1 Short): JPEG Technote #2Photometric (1 Short): YCbCrStripOffsets (24 Long): 8, 175, 342, 633, 2227, 3683, 5112, 6553,...SamplesPerPixel (1 Short): 3RowsPerStrip (1 Short): 16StripByteCounts (24 Long): 167, 167, 291, 1594, 1456, 1429, 1441, 1114,...PlanarConfig (1 Short): ContigXPosition (1 Rational): 0YPosition (1 Rational): 0JpegTables (574 Undefined): ReferenceBlackWhite (6 Rational): There is no YCbCrSubsampling tag present in this file. According to TIFF, Revision 6.0 (1992), the default values of this field are [ 2, 2 ].Charles > From: john.evans@mathworks.com > To: tiff@lists.maptools.org > Date: Tue, 24 Apr 2012 12:26:21 -0400 > Subject: [Tiff] YCbCr/JPEG issue in 4.0.1 > > I'm seeing an issue in 4.0.1 regarding jpeg-compressed YCbCr tiffs that > wasn't > present in 3.9.5. A 4.0.1 client such as tiffinfo doesn't seem to print > out > the TIFFTAG_YCBCRSUBSAMPLING value on a tiff when the library has to > "sniff out" > the subsampling values from the JPEG datastream, whereas a 3.9.5-based > tiffinfo > does. "quad-jpeg.tif" is an example file where this happens. > > When digging deeper, the TIFFGetField library routine fails on the > subsampling > tag on quad-jpeg.tif in 4.0.1 whereas it succeeds in 3.9.5. I've tried > debugging further, but I get a bit lost when the library code gets into > the > TIFFFieldSet macro, which is where TIFFGetField is failing. In 3.9.5, > the > code looks like it would continue on into JPEGVGetField, but in 4.0.1 this > > function is missing the case for TIFFTAG_YCBCRSUBSAMPLING, which makes me > think that I'm missing something blindingly obvious here? > > I did NOT run the configure script in 4.0.1 with "--disable-check-ycbcr- > subsampling" option :-) > _______________________________________________ > Tiff mailing list: Tiff@lists.maptools.org > http://lists.maptools.org/mailman/listinfo/tiff > http://www.remotesensing.org/libtiff/