Legacy ImageMagick Discussions Archive

Hi,


question
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I have a question about JPEG compression using the convert command-line utility. I do not know if the images I use will be JPEG2000, JPEG or a mixture (I suspect this is so).

For each of these images, I wish to take a given JPEG file, infile.jpg, and produce a set of output JPEG files having the following compression percentages:
10,20,30,40,50,60,70,80,85,90,92,95,98. They would have names like outfile10.jpg, outfile20.jpg, etc

I see I have to use the -quality option. However, I do not understand how to map to these percentage values. i have looked at the documentation (http://www.imagemagick.org/script/comma ... hp#quality) but it does not say.

Any help would be greatly appreciated

Thanks

Matthew

platform
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I am using convert at the command-line on a 32-bit Ubuntu Linux system (uname -a ->Linux cseepg12y 3.13.0-53-generic #89-Ubuntu SMP Wed May 20 10:34:28 UTC 2015 i686 i686 i686 GNU/Linux)

$ convert -version
Version: ImageMagick 6.7.7-10 2014-03-06 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenMP

see -define jpeg:extent={size} at http://www.imagemagick.org/Usage/formats/#jpg_write

alternately use my script downsize, at the link below, which iterates to find the given file size