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July 2007
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2007.07.05 19:29 "Re: 16-Bit-Per-Channel Lossless Compression", by Stephen Carlsen
Joris et al, Indeed, so in my compression tests I used single-row tiles. This may not be optimal for all applications, but it is where I get the best import and display performance with page layout programs, and, amazingly, my compression ratios were about the same as when I tried more-square tiles. YMMV, of course... Best regards, Stephen At 8:30 PM +0200 7/5/07, Joris wrote: >Stephen, > >Stephen Carlsen wrote: >>Separating 16-bit data into byte planes before compressing seems to >>be very effective. I get 40,882,548 bytes using the simple approach >>of applying LZW (with predictor) to the high byte plane and no >>compression on the low one. > >The problem here is that it is no longer sequential, i.e. a decoder >or encoder can no longer stream out line/block by line/block (where >block is a very limited chunk of compressed data, as line is a >minimal chunk of image), whilst streaming in the data as needed >block/line by block/line, and maintaining only a mimimal buffer in >between. Instead, total buffering of complete striles becomes >necessary in this scheme. Therefore, it doesn't scale well (problem >with LibTiff approach and huge striles), or doesn't stream well >(problem with minimal buffering maximum throughput approach of >AsTiff). > > >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 >_______________________________________________ >Tiff mailing list: Tiff@lists.maptools.org >http://lists.maptools.org/mailman/listinfo/tiff >http://www.remotesensing.org/libtiff/