Painting application on the GPU

Hi,

I have been playing around with a CPU implementation of a painting application. The tools I want to implement are pretty basic paint, floodfill, eraser and do/redo. My platform is android so I'm using opengl-es.

My implementation is pretty slow when using large images because CPU/GPU work is not balanced and we have the always dreaded bus bottleneck when downloading/uploading textures. I could try to implement some kind of "Tiled" implementation to split the canvas I want to draw on in smaller textures and consume gpu bandwith in a more optimized way but I think it is time to start learning a bit about how to do this on the gpu.

Could anyone be so kind to point me in the right direction here? I don't want/need the exact implementation but some guidelines on how to implement this tools. Paint seems to be pretty straightforward. I think I could use my drawing line code to generate geometry for my lines, but for example, how could I implement the eraser tool? I guess some kind of black shading program magic could do the work, but again I'm lost on this subject.

Come'n guys let's discuss best techniques to build this little app.

P.D. I know there are some painting apps templates on the asset store but I would like to implement this myself. On the other hand, most of them are not taking advantage of the gpu.

Cheers.