CMYK color shifts

[narph]

I'm using ImageMagick-6.5.4-8 via command line Linux.

I have noticed when I render colored text in a CMYK color space, the resulting text is not the same CMYK value that I specified. I'm working on a print project, so exact CMYK values are necessary.

This is a simplified example that yields my issue:

convert -colorspace cmyk -background white -fill 'cmyk(10%,100%,50%,0%)' -size 200x50 -caption:'test' test.pdf

The resulting text's color gets shifted from (10%,100%,50%,0%) to (0%,100%,44%,10%). They look close enough on the screen, but the printed output is very different for some colors.

Is there a work around to force or trick the font rendering routines to stick to my CMYK values?

Thank you.

[fmw42]

you probably need to use profiles to maintain good color translation.

[narph]

Yes, Thank you. It's not a perfect solution, but it will get the result I need.

One of my goals was to overlay a rich black text without shifting other color numbers in the image.

I ended up making a separate 'black' text layer using parenthesis and applying a cmyk -profile transformation to just that layer in the parenthesis. With the right cmyk profile, the black text gets converted to rich black. Then I use -composite to merge the rich black text layer into my original image. The base image doesn't get converted by the profile command if you use parenthesis, which is perfect for me.

Some of the other cmyk colors I'm trying to hit will take some experimenting with a custom icc profile, but I am encouraged by the results so far.