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November 2008
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2008.11.22 01:05 "Re: LZW compression in your legacy app", by Kevin Myers
> Kevin, > It isn't clear from your posts which, if any compression schemes your > legacy app supports. LZW was patented by Unisys for a long time and many > versions of LIBTIFF disabled the code to support it. You might try the -c > packbits option with tiffmedian to see if it can read files compressed > with that algorithm or run your newly minted palettized images through > tiffcp to apply one of the other algorithms to see if the issue was the > Unisys patent on LZW compression. > > Richard Yes, the legacy app does support a few compression schemes, including G4 for black & white and packbits for grayscale and color. It definitely wouldn't surprise me if the LZW patent was the reason that LZW compression was omitted. The legacy app also doesn't support either the old or new implementations of JPEG in TIFF for color images. As far as I know there were never any legal issues involving JPEG compression, but perhaps JPEG compression might have been excluded to avoid the need for libjpeg or something along those lines. Unfortunately, packbits compression doesn't really seem to help very much with typical grayscale and color images that I work with, and of course G4 compression can't be used on those. The legacy app also only supports TIFF images, so jpeg files, png files, etc. aren't an option either. Kevin M.