Convert color of an image from rgb to cmyk

[jeremydouglass]

For a related approach to separate C M Y K channels, see:

Best way to do this: tint(C, M, Y, K)?

I think @Jakub is right. The reference for all the blend modes: blendMode() or maybe blend(). You can use SUBSTRACT or MULTIPLY and try another ones. They are similar to Photoshop blending modes. Mathematically, RGB converts directly to CMY, with no need of Black (K). Theoretically, the mix of C+M+Y should result in black. We only use Black on printing because inks are not perfect, so black ink gets better results for contrast and other details. So, when you add black ink, you need to do the m…