[joshd]

noidi's yotube link explains it pretty well. It searches the rest of the image for sections that are similar to the edges of the deleted area and extrapolates from there. I imagine for large deleted areas this would have to be done multiple times to build up the deleted area. It woudl be kind of lie markov chains, but for image data.

The current patch tool in Photoshop can already adjust contrast and hue to make a patch source match the patched area, so when the algorithm is searching for similar areas to use as a source it can just focus on the image details and not the lightness or actual colours.