pbmmask

creates a mask bitmap from the outline of shapes in a PBM image

Create mask from bitmap edges

$ pbmmask [input.pbm] > [output.pbm]

Expand mask by pixels

$ pbmmask -expand [2] [input.pbm] > [output.pbm]

pbmmask [options] [file]

pbmmask creates a mask bitmap from the outline of shapes in a PBM image. Useful for creating selection masks or outlines. Part of Netpbm toolkit.

-expand n

Expand mask by n pixels.