Erasing canvas images to transparent
Posted on 2002-04-29
I have two layered Paintboxes on top of a black panel, making a graph of sorts with little square nodes and connecting lines. I want the user to click and drag the nodes, so I need to erase and re-plot them repeatedly. Likewise with the lines. I rely on the initial transparency of the paintboxes to see what is beneath. How do I make existing pen and brush images transparent? Drawing the panel color simply obscures everything.