ID:2922233
 
(See the best response by Meme01.)
Problem description:
I'm trying to essentially cut an icon in half diagonally, erasing every pixel in one of the halves. My initial thought was to use Blend(I,ICON_SUBRACTION) but this is leaving me with wonky results. Is there a better way to go about this?
Best response
You'll want to use Crop().
I did not know that was a thing! Thanks!
It looks like it'll take a combination of Crop() and Blend(). You'll want to do a loop that systematically crops the original icon line by line.

And as you do so, blend it to a new blank icon.