smearing or onion skins

Does anyone know where i can see some code that smears (or blurs) some lines or textures. Help would be great. I have thought that maybe glReadPixels and modifying would work but i want the fastest approach as well.
Thanks,
Brent

Look in the GLUT examples for the convolve.c and accconvolve.c. But that’s probably not the fastest approach using the accumulation buffer.