I want to fill an area in Gimp but I keep getting pixels on the border. I would like the color to melt together. See below. Left is what I got. Right is what I want.
In both images there is a black line with a red filling. In left image the pixels between the line and the filling are gray. The filling was white before so the black line is fading into white background resulting in gray pixels. But now I want the black line to flow into the red color as you see in the right image. There we have a black line, then black/red pixels flow into the red filling. No gray pixels in between.