Edge Tracing logic.

matt_4013

hi guys, I'm having a bit of a problem with getting the logic worked out for a script. I need to trace lines on an image, get the coordinates of each pixel in the line. So the way I thought to do this was using an edge tracing algorithm. What I'm doing is reading through each pixel until it finds the specified colour and then I want to follow the coloured pixels around. Now, I'm wondering how I would get it to continue. I thought recursive functions, but that seems kind of messy.

Any ideas?

bubblenut

Never done this myself before but just had a quick read around and think, and here's a coupld of point's you might want to think about.

How much accuracy do you need? Are you dealing with text recognition on large, simple text (for example) or something far more complex?
Are the edges going to be mostly straight?
What is the contrast at the edge like? Will it always be similar?
How important is the speed?

I haven't seen any scripts around for this in PHP but there seems enough info out there to build your own. It sounds really interesting and I'd deffinately be up for coming in on a Sourceforge project or the like.

Bubble

Weedpacket

It would be crushingly slow; and it makes no provision for "approximately the same" pixels (though it could probably be hacked in), but I sketched something out (for region finding) here. The edges are of course where different regions meet.

You'd probably be better off with some sort of command-line-driven utility, though.