Hey guys, I know this topic has been inactive for a while.
But I've got some work in progress that I'd like to share.
I am working on a tool that automatically generates Normal Maps with only a sprite file as the input image.
Of course, the resulting Map isn't as perfect as a hand drawn one, but in cases where you have a large number of sprites, like animation frames or body parts of a character you want to animate with a tool like Spriter, the quality should be good enough.
This is the Normal Map, Depth Map, Ambient Occlusion Map and Specularity Map, that my Tool (Sprite DLight - hopefully soon on Kickstarter) produced from the original sprite in a matter of seconds: (downscaled from 512x512px)
Seems like the original hand painted normal map's Red Channel was inverted. My tool also has various fine tuning options like Inversion of the Channels, Intensity and Volume Boost Sliders and a lot more.
If somebody has an atlas of bodyparts for an animated character he wants to try out with dynamic lighting, you can send me your art and I can see if the tool can generate a nice normal map for it.