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May 2010
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2010.05.11 15:49 "Re: Tiff with varying bit depths", by Frank Warmerdam
Thomas Richter wrote: > Hi folks, > > I currently have a need to read and write TIFF files with a varying bit > depth. To be specific, this is a BGR565 image packed into TIFF: > > $ tiffdump out.tif > out.tif: > Magic: 0x4949 <little-endian> Version: 0x2a > Directory 0: offset 8 (0x8) next 0 (0) > ImageWidth (256) LONG (4) 1<64> > ImageLength (257) LONG (4) 1<64> > BitsPerSample (258) SHORT (3) 3<5 6 5> > Compression (259) SHORT (3) 1<1> > Photometric (262) SHORT (3) 1<2> > StripOffsets (273) LONG (4) 1<140> > SamplesPerPixel (277) SHORT (3) 1<3> > RowsPerStrip (278) LONG (4) 1<64> > StripByteCounts (279) LONG (4) 1<8192> > SampleFormat (339) SHORT (3) 1<1> > > > Obviously, the library does not support this, but what are my options if > I need to read this file? I'm not too keen to write a tiff-parser > myself, unless I really really have to - and - I afraid - I really > really have to read this file in one way or another. > > Is there a way to get at least hands on the raw stripe data without the > lib falling over? Failing that, what is the patch acceptance policy > for libTIFF? Would you accept a patch that adds support for this, > probably in a limited way? Thomas, Have you investigated using TIFFReadRawTile() to read these tiles? At what point does libtiff fail with this file? I don't anticipate the regular decompression/decoding logic working with such a file in the near future, but I would like to see it be possible to fetch the raw tile/strip data without too much difficulty. Can you make one of these files available? Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent