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March 2006
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2006.03.04 03:12 "Re: LZW Compression with 16-bit TIFF", by Bob Friesenhahn
On Fri, 3 Mar 2006, Frank Peters wrote: > > With 16-bit tiff files, however, the compressed file is > actually LARGER. For example, using the above command > a 36 megabyte 16-bit tiff file will "compress" to about > 46 megabytes. For the other possible options, "-c lzw:1" > and "-c lzw", the results are essentially the same. The > compressed file is always significantly larger. > > If I use "-c zip" as the option, 16-bit files are reduced > somewhat (from 36 Mb to 34 Mb). > > Is there possibly a bug in the 16-bit lzw code or does the > fault lie elsewere? 16 bit data can be difficult to compress. Have you tried enabling horizontal differencing? TIFFSetField(tiff,TIFFTAG_PREDICTOR,2); Bob ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/