This plugin allows you to unseparate (recombine) individual PNG files (up to 6 files) and preview them in GIMP as they would be printed - for example on a 6-color silkscreen press. This is useful when preparing 1-color screens in GIMP or other programs, since you can get a reasonable representation of how they will look when printed atop one another.
This plug-in requires Python. Please do not ask how to install Python support for GIMP - search the forum (I'm looking at you, windows users ;)
Part of a set of plug-ins called 'Silkscreen Tools'. Installs to Filters->Silkscreen Tools->Unseparate PNGs
Parameters are pretty straightforward:
Substrate Color: Color of the printed item (t-shirt, banner, etc)
Ink Opacity: Fill opacity of the ink channels
File 1: First PNG file
Color 1: Ink color for file 1
After running the plugin, selecting files and colors - look into the Channels dialog. There you will find your recombined PNGs as spot channels, and you can edit/tweak each channel as desired. Hide "Layer 0" and hide all channels except one to view/edit that channel as a grayscale image.
EDIT: latest version freezes the undo stack to reduce memory usage.