Explain color profiles to me please

Question

I'm dynamically building PDFs with Perl. I've been instructed to make all my pdfs use CMYK instead of RGB and that I should use color profiles to do it. I understand what colorspace is and how to do the conversion but I dont understand why. Can someone explain color profiles?

I think the following is the same question asked 3 different ways:

1. I understand that the printer print with Cyan, Magenta, Yellow, blacK instead of Red, Green, Blue. But why does that matter? Surely printers can convert between CMYK and RGB with a formula?

2. I don't understand how using color profiles during the converstion from CMYK to RGB helps. Surely there is one formula for converting from RGB to CMYK? Why is it good to specify a RGB color profile and a CMYK color profile?

3. What is in a color profile file? Why is it binary? Why is it so big (ISOcoated_v2_eci.icc is 1.8Mb)?

Answer 1

Printers can convert between CMYK and RGB. They do have a formula. The problem is they all have a different one :)

Seriously though, this topic is very broad, and not really programming related. Reading a book or basic tutorial might work best. Wikipedia can give some first aid:

• CMYK Color model

• ICC Profile

• Color management

• Oh, and a nice one on the graphic design SE: What are color profiles?

Also, Googling introduction to color management turns up some interesting-looking tutorials like this one.

if you have some more detailed questions, I'd say the right place for most of them is Graphicdesign.stackexchange.com.