Unity is not recognizing updates I make to a material's source image.

Hello there,

I am making materials to put on low-poly building models meant to be viewed from a distance, stylized so that their edges glow like vector graphics, and things went smoothly for a while. At some point, though, a problem occurred, and it had to do with things erased. I edit the materials in Gimp, but so far as I can tell, the problem is not on that side. So instead, I will take a few screenshots of my Unity editor to detail the problem.

The first image displays in the scene view, the building with highlights on the edges. Note, though, that there are some other lines I put in the wrong place, and this is the source of my problem; I tried erasing such lines in Gimp, and succeeded, but they have not erased in Unity. Also visible in this image are the Material, selected in the Materials folder, and a larger shot of that material in the Inspector.

The second image shows Unity's interpretation of the PNG file that is used as that Material's Emission Map. The same redundant lines are present.

The third image, though, is what I get when I click the "Open" button in the inspector, and it illustrates my conundrum. As this demonstrates, I erased those redundant lines in Gimp. The image file, viewed in most contexts, no longer has them. But Unity still keeps them in.

So what could be wrong here?

 

I have an update: Contrary to what I stated earlier, it does seem that this issue relates somewhat to Gimp. This is because I can make those lines disappear if I export to a PNG with their layer disabled. But I still have no idea why those lines are still on that layer, as I erased them. Also, the erased lines are still invisible anywhere except in Unity.

 

New update: The erased pixels only remain in the RGB map channels; not the alpha channel. Any idea why?