What ICC profiles does Adobe Illustrator use to convert between RGB and CMYK in its color picker?
What ICC profiles does Adobe Illustrator use to convert between RGB and CMYK in its color picker?
Question
I'm trying to understand Adobe Illustrator's color conversion method between RGB/HSB and CMYK. I'm pretty sure they use ICC profiles to do the conversion, and they make a bunch of ICC profiles available for download (http://www.adobe.com/support/downloads/detail.jsp?ftpID=3680).
I can't match the conversion using a combination of those profiles to Illustrator's color picker.
What RGB and CMYK ICC profiles does Illustrator use in its color picker?
Popular Answer
This is a pretty old question, but based on its unanswered status and number of up votes and views I thought I'd take a crack at it. Based on your question and the additional comment about doing the conversion on a programmatically on a Linux server, I did some hunting around. There is a Ruby library called ruby-pdf that does colour conversions for handling PDFs. In the docs for the library's colour tools it discusses using the tools for conversion. Interestingly, there is this tidbit:
# Adobe PDF Display Formula
r = 1.0 - min(1.0, c + k)
g = 1.0 - min(1.0, m + k)
b = 1.0 - min(1.0, y + k)
See here for the reference: http://ruby-pdf.rubyforge.org/color-tools/doc/classes/Color/CMYK.html
Note this comment: "Converts the CMYK colour to RGB. Most colour experts strongly suggest that this is not a good idea (some even suggesting that it’s a very bad idea). CMYK represents additive percentages of inks on white paper, whereas RGB represents mixed colour intensities on a black screen."