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Compress JPG with ImageMagick
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| convert -strip -interlace Plane -sampling-factor 4:2:0 -define jpeg:dct-method=float -quality 70% source.jpg output.jpg |
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From: http://stackoverflow.com/questions/7261855/recommendation-for-compressing-jpg-files-with-imagemagick
From @Fordi in the comments (don't forget to thumbs up his comment if you like): If you dislike blurring, use -sampling-factor 4:2:0 instead. What this does is reduce the chroma channel's resolution to half, without messing with the luminance resolution that your eyes latch onto. If you want better fidelity in the conversion, you can get a slight improvement without an increase in filesize by specifying -define jpeg:dct-method=float - that is, use the more accurate floating point discrete cosine transform, rather than the default fast integer version.