Since last week I've been working on a small image editor which is supposed to increase the asset quality of a game I'm working on by letting me add details and shading to sprites and textures without too much effort.
This is mainly achieved by editing a bumpmap and then baking the resulting specular light on top of the very simple original image. It works quite well so far, and while the output certainly isn't perfect, it's a step into the right direction.

General layout of the editor: Colored image on the left (the red/yellow squares here indicate that certain parts of the image are masked out and hence will not affected by the drawing tools), bumpmap on the right
Generally, the workflow looks like this:
1. Create a very rough first draft of your image with any image editing software (say MS Paint)
2. Import into the editor
3. Draw bumpmap
4. Adjust light settings until the desired look is achieved
5. Save the project, which will automatically export the final composition as well as the bumpmap

Left: Simple bed shape made in Paint; Right: Result after spending about 3 minutes on it with PainTex
This
video demonstrates how such a bed sprite can be obtained in the software.
Right now there are quite a few drawing tools available to edit the bumpmap, most notably a standard brush, lighten/darken, blur and a pattern brush - the latter can be used to apply certain predefined textures to the bumpmap as depicted in the image below or in
this video.

The two "snake" shapes were created with a standard brush, the four texture types in the corners were added using the pattern brush.
Finally, the editor allows editing the image and bumpmap using
multiple layers. While one layer is enough in many cases, sometimes you want to divide individual aspects of the bumpmap. Each layer has its own bumpmap as well as its own light settings. One way to use multiple layers is to define the general structure of an object in layer 1, and use the second one to add the finer details. This way high and low frequency aspects of the texture can be manipulated independently.
This concept, as well as the useful
color gradient tool are demonstrated in the video below.
Obviously the GUI isn't final yet, and generally controls and interaction aren't perfect. I might fix a few things, add a bunch of tools if any useful ones come to mind, make sure it's a bit more appealing visually and ideally release it sooner or later. Can't promise anything though, I've got a lot of things to deal with other than this, and for now I'm happy I got it to a usable state before this weekend's Ludum Dare competition (which I intend to take part in, probably using this editor to create my assets).
Any kind of input and feedback is very welcome. Otherwise I'll just update this thread every now and then - if there will be any updates, that is.
- Shellfish Games
Sidenote: The patterns (metal, bricks and cracks) used to create these images were taken from different sources and are not made by me. I just had them stored somewhere on my hard disk, so I'll have to replace them eventually.