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June 2010
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2010.06.23 17:14 "Re: LZMA2 codec for libtiff", by Bob Friesenhahn
On Wed, 23 Jun 2010, Scott Ribe wrote: > On Jun 23, 2010, at 10:16 AM, Andrey Kiselev wrote: > >> Compression is better than the one with Defalte codec >> for almost all data files I've tried. Sometimes it is MUCH better. > > You might play with bzip. Same advantages re open implementation and > patent-free. In my (very limited) tests, compression was only > slightly worse than lzma, and performance was much better. While I have not tried Andrey's patch, I have done testing in the past of bzip2 and lzma on whole image files and found that (for the images I tested) lzma did not seem to offer much compared with bzip2. Results are quite different with ASCII text where lzma is clearly a win. There may be particular images where lzma is a clear win. It is useful to do a study of file size, compression times, and TIFF predictor influence to understand the issues. My interest tends in a different direction. It would be nice to have a very fast compression algorithm in TIFF which compresses faster than LZW or gzip yet is similar to 'gzip -3' compression levels. This compressor could be the compression used in lzop. The value of this is that uncompressed TIFF files can be excessively large and burdensome for system I/O whereas compressors are often quite CPU bound. Using the right compression algorithm may improve read/write performance for large files. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/