This script creates images via the exact process invented by Michael Orton. You need two exposures of a scene, one at an exposure value of +1, and one at an exposure value of +2.
More information is available at: my blog.
These are most easily obtained by taking a single raw photo of a scene and then producing two JPG images with appropriate exposures.
Load the +1 EV image, and run this script from Filters->Artistic->Orton, and you will be prompted for the filename of the +2 EV image. Choose this, press OK, and you will get an Orton image.
The Orton processing is especially good for landscapes and flowers.
(per user request relicensed this under the MIT license)