I'm trying to test this little graphics program I wrote, and I want to be able to draw configurations of solid colored shapes in Gimp, and then import them into my program for testing. It's important that the shapes be absolutely solid colored, and not have any weird non-uniformities in them.
A complication I'm having by trying to make these images in Gimp is that even when I uncheck "feather boundary" and change the Edit > Stroke Style width to 0 px, I still get a boundary around the ellipse, e.g. the picture below. So in the picture below, I took the exported ellipse image from Gimp, then did an MS paint fill of black on the interior and exterior of the ellipse, and I get the observed boundary on the right.
I'd appreciate any thoughts for how to totally prevent this from happening, so that there's absolutely no boundary or transition region at all.