For my 2D game, I plan to use sprites in which every image has both a color texture and a normal map of equal resolution. This will allow me to fake 3D lighting for all of the 2D game entities. In order to make it as easy as possible for the artists to generate these normal maps, I would like to provide them with a tool in which they can load an image and move pixels on the image up and down to simulate contours. From this depth information the tool would then be capable of generating the normal map. Does such a tool already exist, and if so is it free? If not I will write it myself, but I thought it would be prudent to see if the work has been done before prior to investing the man hours.

Sounds cool, nvidia has made a plugin for photoshop that converts images
to a normal map, but i guess you want more. So you better start codeing :-)

It sounds like you can just have them paint heightmaps (grayscale) for the sprites and convert them to normal maps using the Nvidia plugin.

Hmm, that plugin looks quite helpful, and having the artists paint displacement maps would be much easier than creating my own 3D tool. Although having a 3D representation of the displacement would be nice, it probably isn't worth the investment now that I see that there is an alternative. Thanks.