After i have grabbing with both hands in the forum a small summer gift (I hope it will be appreciated).
You find the scanline floodfill algorithm using stack instead of recursion.
I converted the version I found in internet from C++ to GlBasic.
Compared to the standard version this is much faster about 10-15 times.
When you start the program for the first 10 seconds, the standard (more slow) version is executed and after the scanline version.
The program uses my FASTMEM2SPRITE version (which you already sent a while ago and which I have now improved), but you can comment the command and activate the standard MEM2SPRITE to appreciate even more the change of speed.
Let me know