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Once again, but different?: RGB to CMYK conversion

Posted: 2009-10-26T07:56:22-07:00
by coruscant
Hello All,

I already have read several hundred posts on different websites regarding the conversion of a jpg photo from RGB to CMYK colorspace with ImageMagick.

The most common way (if I count the suggestions in various posts) to do this is:
convert original.jpg +profile icc -profile AdobeRGB1998.icc -profile USWebCoatedSWOP.icc -strip converted.jpg
Explanation:
+profile icc: removes icc profiles form the file if there are any
-profile AdobeRGB1998.icc: use this icc profile for the source file ("original.jpg")
-profile USWebCoatedSWOP.icc: use this profile for the destination file ("converted.jpg")
-strip: do not include profile in the destination file to keep file size reasonable

The result in terms of colors is more than sufficient. I like the way it is done. But here comes my problem: The overall quality (beside the colors - they are o.k.) of the image becomes really horrible.

Look at these files:
http://www.casamexico.at/test/original.jpg
http://www.casamexico.at/test/converted.jpg

The original one was exact, the converted is just a mess. Does anybody know why is this and how to prevent this?
My ImageMagick Version: ImageMagick-6.2.8.0-4.el5_1.1

Thanks in advance,
Coruscant.

Re: Once again, but different?: RGB to CMYK conversion

Posted: 2009-10-26T17:34:53-07:00
by anthony
set a higher -quality setting -quality 90 for example.

Im defaults to a quality of 75.


WARNING: reading and saving JPEG will always cause some loss of quality. JPG is a file format designed for the 'final display image' it should not be used as intermediate images if it can be helped.