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February 2011
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2011.02.12 22:51 "Re: JPEG issues with tiffcp", by Bob Friesenhahn
On Sat, 12 Feb 2011, John Brown wrote: > > It is good that it automatically uses the new JPEG instead of OJPEG when > it encounters OJPEG. However, since tiffcrop decompresses the input and > tiffcp does not (that was something that I wondered), I expect that > tiffcrop will be much slower than tiffcp. In fact, the reason that I > have not given up on libtiff even though GraphicsMagick produces perfect > results is that GraphicsMagick is very slow. tiffcp produces 13 > documents containing a total of about 30 images in less than a second, > but GraphicsMagick takes four seconds. Still, correct output is more > important than speed. I don't think that there is any alternative other than to decompress and recompress the JPEG data since OJPEG and JPEG are different. It might be possible to automatically estimate the JPEG compression parameters which produce minimal/no quality loss due to recompression. There is code in GraphicsMagick which does that for ordinary JPEG files but not for JPEG in TIFF. > It would be inefficient to run tiffinfo on every image > when I expect the overwhelming majority to be monochrome G3 or G4. Tiffinfo is quite fast. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/