Either you're an artist or a programmer. Of course, there are multi-talented folk out there that can do both well, but if you only fall into the latter category and wish you could just "code" pictures to your specifications, then a new, shader-based image editor called Shadron is worth a look.
Created by one Viktor Chlumský, Shadron uses GLSL (OpenGL Shading Language) shaders to manipulate images — and a great deal more, going by the program's description.
In basic terms, a shader is a program that runs on your GPU and instructs it on what to do with a pixel (or vertex). It can be as simple as modulating the colour, to sampling adjacent pixels and averaging the result — blurring, essentially.
A great deal of Photoshop's image filters can be implemented as shaders, so being able to hand-craft such effects is a powerful advantage indeed. If you're curious about what Shadron can accomplish, the lead video does a good job of showing off its abilities.
It goes without saying that if you don't know the first thing about programming or shaders, then Shadron isn't going to be of much use to you. But for programmers, particularly budding game developers, Shadron could be the answer to a number of your asset creation woes.
The app is available direct, or on Steam if that's your preference.
Shadron [Official website]