PintaProject/Pinta — pull request #19 by jpobst (2012-05-01 22:54:15+00:00)
Title: Only store difference between 2 surfaces for history.

Implement a "SurfaceDiff" class that only stores the pixels that actually changed between 2 surfaces. When used for history, this can result in some very large memory savings. For example, Paintbrush operations, which are generally much smaller than the full canvas, now require 1-2% of the memory they used to.