I don’t know of any C# API or library that can achieve this. However, if you have enough C/C++ knowledge to build a wrapper for C#, I see two options: Windows Color System (WCS) (part of Windows) LittleCMS The System.Windows.Media namespace is very limited. There’s probably a powerful engine (WCS?) behind it, but just a … Read more
This answer is not for Illustrator, but for ‘some other tool’, namely Ghostscript (download gs871w32.exe or gs871w64.exe). Ghostscript allows you to ‘re-distill’ PDFs (without an intermediate conversion to PostScript, the dreaded ‘refrying’ detour). Try this command: gswin32c.exe ^ -o c:/path/to/output-cmyk.pdf ^ -sDEVICE=pdfwrite ^ -dUseCIEColor ^ -sProcessColorModel=DeviceCMYK ^ -sColorConversionStrategy=CMYK ^ -sColorConversionStrategyForImages=CMYK ^ input-rgb.pdf And if you … Read more
There is a lot of good stuff in the existing answers already. But none of them is a complete solution that handles the different kinds of CMYK JPEG images. For CMYK JPEG images, you need to distinguish between regular CMYK, Adobe CMYK (with inverted values, i.e. 255 for no ink and 0 for maximum ink) … Read more
The conversion from RGB to CMYK is dependent on the physical device/process being used to lay down the CMYK ink. These are represented in software as Color Profiles. ICC and ICM color profiles of physical devices determine the resulting colors. If you are not concerned with true representation on a physical device then use the … Read more
sdaau, the command you used for trying to convert your PDF to CMYK was not correct. Try this one instead: gs \ -o test-cmyk.pdf \ -sDEVICE=pdfwrite \ -sProcessColorModel=DeviceCMYK \ -sColorConversionStrategy=CMYK \ -sColorConversionStrategyForImages=CMYK \ test.pdf Update If color conversion does not work as desired and if you see a message like “Unable to convert color space … Read more
As Lea Verou said you should make use of color space information because there isn’t an algorithm to map from RGB to CMYK. Adobe has some ICC color profiles available for download1, but I’m not sure how they are licensed. Once you have the color profiles something like the following would do the job: import … Read more