[Image-SIG] Flood fill with threshold

[Yury V. Zaytsev]

Hi!

I have an image with certain areas that are bounded by color boundaries.
I'd like to have a program that flood fills the region with a certain
threshold after the user clicks on the image and records the pixels that
belong to this area.

I found out that Gimp's flood fill tool with threshold 48 does exactly
what I want. Has anyone got a clue on what is the algorithm they used?

All I could find after short Googling are flood-fill algorithms where
you give the target color explicitly which I do not want to do, because
I don't know it and also it varies slightly across the border.

Is there any implementation I might refer to other than downloading
Gimp's source code and trying to make sense out of it?

Thanks!
 
-- 
Sincerely yours,
Yury V. Zaytsev