From the help: Enlarge by synthesizing a concentric band that matches the edge, maintaining perspective. Works best for small enlargement with natural edges. Undo a Crop instead if possible! Requires separate resynthesizer plug-in.
This is the initial version, lightly tested.
Examples show that the results are not always acceptable: undesirable artifacts appear in undesirable regular patterns. In other words, hit and miss. The attached examples are the result of Uncrop at 20 percent.
It would work better if the resynthesizer plugin is modified to synthesize directionally starting from the edge. (As it is now, it synthesizes pixels in the target area in a random sequence.) But for now, I don't want to post an update to the resynthesizer plugin itself.
As with other plugins that call the Windows version of resynthesizer plugin, it needs a slight modification to work on windows. See instructions in the comments for the Heal selection plugin.