http://research.graphicon.ru/image-processing/gml-matting-6.html

Introduction
GML Matting is FREEWARE plugin for Adobe® Photoshop® and compatible applications. GML Matting is a cutout tool to help separate object from background. Interface of the plugin is similar to that of Photoshop Extract utility while the algorithm used usually produces better result. For Paint Shop Pro users it can become the essential matting plugin since Paint Shop Pro has no built-in matte extraction functionality.

GML Matting uses color statistics obtained from user-specified trimap and produces alpha matte as well as restored foreground color. Its result is stored in current layer's color and alpha channels.