“Paul Harrison’s Resynthesizer is a texture-synthesis plugin for
the GIMP. Sure, you can use it for simple things like creating
seamless, tileable textures, but you can also have it remove any
object from a picture and automatically replace it with a synthetic
background, with impressively professional-looking results.“To get started, visit Harrison’s Resynthesizer page and
download the package. The latest release is 0.13, currently
available as source code for Linux and a compiled binary for
Windows. The 0.12 release is available as a binary for Mac OS X,
and can also be found pre-packaged with Gimpshop…”