There's also a Graphic Design Stack Exchange:
Graphic Design is for questions targeted toward 2D design professionals, students, and enthusiasts.
This includes questions about:
Graphic arts theory and history; "Why" we do what we do and not necessarily the "how" in logo design, fonts & typography, visual communication
Both are computer software — well, Super User is the place to ask, definitely.
Check out our existing questions for:
If you instead want to do image processing using some programming language, Stack Overflow would be better.