http://rosettacode.org/wiki/Canny_edge_detector currently does not have a J implementation.
Worse, the task itself is somewhat ill-specified, with a variety of open-ended possibilities. This suggests, to me, that it would be better handled by someone who works images and/or edge detection in some other contexts (because this kind of experience would helpfully inform the implementation decisions). Anyone interested? Thanks, -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
