ppmrelief – run a Laplacian relief filter on a portable pixmap
Reads a portable pixmap as input. Does a Laplacian relief filter, and
writes a portable pixmap as output.
The Laplacian relief filter is described in “Beyond Photography” by
Holzmann, equation 3.19. It’s a sort of edge-detection.
Copyright (C) 1990 by Wilson Bent (firstname.lastname@example.org)
11 January 1991 ppmrelief