Stampify renders the current image as a postage stamp. The filter provides the semi-circles around the edge that represent the torn perforation holes found in stamps.
The Paper, and Hole color settings can be accessed directly, by clicking the color well, or by using the FG, and BG buttons to fetch the currently selected colors from the Toolbox.
The Diameter setting configures the number of pixels that make up the diameter of the holes.
The Gap parameter sets the gap, in pixels, between the perforation holes.
The Marg setting affects the gap between the rendered layer, and the perforations.