Hi everyone,

I'm trying for days to solve the following :
How to change the alpha value of some pixels in a still picture depending on the mouse or tablet location ? I can't succeed to find an object doing this in GEM.
My goal is to simulate a classic erasor as found in the Gimp for example , or photoshop or whatever.
Any idea ?
Best

fastest (processing-wise) way is to write a multitexturing shader to do this

texture 0 is input image, texture 1 is transparency, paint in texture 1 to erase texture 0.

you would need multipass rendering and pix_snap2tex to catch the drawing actions into texture 1. and you'd need to learn GLSL fragment shaders (which isn't too hard).

Thanks a lot Claudius for answering. I'm going to try out your solution.
Best