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May 2010
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2010.05.11 19:19 "Re: Tiff with varying bit depths", by Thomas Richter
Igor Skochinsky wrote: > Hi Scott, > > The values make perfect sense to me. > The image is 64x64 pixels, each pixel is 16 bits, so the strip size is > 64*64*2 = 8192 bytes. Pixel data is split into three samples: 5, 6, > and 5 bits for R, G and B. > > Thomas, > > Can you debug TIFFOpen() it and see which check fails? I expect that > if you patch it, you should be able to use TIFFReadRawStrip() or maybe > even TIFFReadEncodedStrip(). The code fails in TIFFFetchPerSampleShorts, called by TIFFReadDirectory (expected), called by TIFFClientOpen (probably unexpected). Thus libTIFF already parses the first directory from TIFFOpen(), which is documented behavior. I also see from "man TIFFOpen" that the "h" flag prevents that, thus I could at least open the file, but then do what? If I cannot read the directory without falling over, how do I get at the bits per sample tag (which I still need, in one way or another). I'm currently using ReadEncodedStripe() - or - ReadEncodedTile(), depending on whether the image is tiled or striped; would be great if I would be able to continue using that, but I nevertheless need the directory content. Is there a way to patch up the directory *after* TIFFOpen(), but before TIFFReadDirectory() sees the file? For example, getting the bits per sample *manually* (without running into TIFFReadDirectory()), then patching that and the number of samples over, then calling TIFFReadDirectory(), and then fixing the mess again when reading the data? So long, Thomas