wow, that would be cool… and I’m thinking pretty tough. maybe you could do a hack like this:

1–start where you click, and assume you’re inside the shape.
2–get the color where you are, and assume the color is the same everywhere in the shape. change the pixel to the desired new color.
3–go left (- pixels in X direction) and repeat until you hit another color, and assume that’s the shape edge. stop.
4–go right (+ pixels in X direction, from original point, do similar change until the other edge. stop.
5–go up one pixel and repeat everything, until another edge. then repeat going down. however, this won’t work all the way unless you’re in the middle of the shape, argh.

Probably there is a much more savvy trick using better edge detection techniques. But this might provide some interesting results, even if it doesn’t always work perfectly. Example: if the shape is mostly closed, but not all the way, will it spill out? With this technique it would, but only in the direction of the break. Etc…

An interesting challenge regardless. Just trying to make something hacked together for it should yield some new tools and insights. Using jit.lcd is probably better, so you can take advantage of the matrix operations. Maybe there’s a combination of several jit.ops which will do most of what you want.

The recursion/stack overflow might not be an issue, as long as you have a comparison operator for each new pixel tested, and you also stop the recursion if X or Y coordinates go below 0 or above your maximum (dimensions of the LCD or whatever you’re using). A [trigger b b b b] where each of the bangs deals with the X+1, X-1, Y+1, Y-1 respectively, and probably a [defer] before the recursion in each. Though I don’t know if the [defer] or a [deferlow] would allow the other trigger bangs to fire before the recursion is done?