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November 2008
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2008.11.22 01:40 "Re: LZW compression in your legacy app", by Toby Thain
On 21-Nov-08, at 8:05 PM, Kevin Myers wrote: >> 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, If they are 'naturally noisy' like photographs then LZW would not help much either. --Toby > 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. > > > _______________________________________________ > Tiff mailing list: Tiff@lists.maptools.org > http://lists.maptools.org/mailman/listinfo/tiff > http://www.remotesensing.org/libtiff/