I just saw this super cute Kantoku illustration at yande.re. Too bad it has compression artifacts. Good thing GIMP has filter called selective Gaussian blur which blurred similar color area but not the edges. With the right setting it can even clean print/paper texture from scanned materials. For anime kind images I usually set the max. delta around 15 to 20, and leave the blur radius to 5 pixels. Here’s the comparison. I still preparing some kind of image viewer for this blog, for now you can right click and open it in new tab/window to see the full size The image viewer is up! Try click the image
Here is the result.