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July 2007
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2007.07.04 18:00 "Re: 16-Bit-Per-Channel Lossless Compression", by Joris Van Damme
Stephen, Stephen Carlsen wrote: > Yup, I've actually done quite a bit of testing, and running LZW with > predictor tends to compress 16-bit digital camera photographs very > little, or even not at all. The problem, of course, is that the low > order bits tend to look a lot like noise. > > I can post some sample files if you like. On one of my images from my > Canon XTi, exported from DNG to uncompressed TIFF (using Lightroom), > the uncompressed size is 57.7 MB, but is 68.8 MB with LZW (plus > predictor) compression. > > Flate tended to generally do worse than LZW, and be a lot slower, in > my testing. Thing is, for photographic data the only real compression that works and make sense both, is lossy compression, is JPEG. Therefore, part of the answer to this problem ought to be more widespread and easier building of a 12bit/channel JPEG compression. That's doesn't cover the really lossy needs (though on photographic data there is not much such need), and it doesn't cover the really 16bit/channel need, so it's only part of the answer. But a vital part nonetheless. Best regards, Joris Van Damme info@awaresystems.be http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html