In my job as a Web Application developer, occasionally designers send me images to place on web sites, which is usually fairly simple. However sometimes I receive images from print-orientated designers, who use Adobe Photoshop to create images in CMYK format. These images are great for printing, however they don’t work too well on the web (most browsers won’t even render CMYK formatted colours), so it it’s usually best to convert them.
The GIMP can’t load CMYK images (yet anyway) , and although Krita can open the images fine, changing the colour type usually results in the colours in the image changing. The only way I’ve found to convert the images on Linux is using ImageMagick.
Firstly, you need to make sure ImageMagick is installed, and “LCMS” is enabled (in Gentoo make sure the LCMS use flag is enabled when emerging it) .
Secondly, you need the Adobe Colour Profiles, these can be downloaded from here . Once you have downloaded that archive, simply decompress it into a suitable location (I use a directory called Colour_Profiles in my home directory ).
Now to convert the image, simple open up a terminal and use this command, substituting cmyk.jpg with the name of CYMK formatted image, and rgb.jpg with the file name you want to create the RGB formatted image as. Also replace “$COLOURPROFILES” with the path to your adobe ICC profiles (from the archive you’ve just downloaded and extracted):
convert -profile “$COLOURPROFILES/Adobe ICC Profiles/CMYK Profiles/USWebCoatedSWOP.icc” cmyk.jpg -profile “$COLOURPROFILES/Adobe ICC Profiles/RGB Profiles/AdobeRGB1998.icc” rgb.jpg
You should now have an RGB version of your CMYK image!