In GIMP, my background is a solid color.1 On top of this background, I placed an image; then I used a patterned fuzzy eraser tool to cut away all of the image which I didn't need.2 And I merged the two layers – believing, falsely, that the fuzzy eraser tool had smoothly blended the two layers together. Later on, when I zoomed in, I noticed that the image has a jagged edge against the background. The layers can't be unmerged.

How do I smoothly blend them together?

  1. enter image description here

2.enter image description here

Here's a version of the merged layers but set in exclusion mode so that you can more clearly see the problem:

enter image description here

  • 1
    Don't merge layers, it's destructive. Also best not to use the eraser tool to delete stuff. Use a layer mask instead - it's non destructive, so if there is a problem you can just edit the mask.
    – Billy Kerr
    Jun 2, 2022 at 13:30

1 Answer 1


When you have a very limited range of values, neighboring pixels jump together from one value to the other making very visible lines (this is known as "banding"). A way to mitigate this on a flat image is to add "spread noise" (Filters > Noise > Spread) so that pixels are no longer aligned.

When you blend layers you can achieve a similar result using the Dissolve blending mode instead of the Normal one: pixels of the composite image are a random pick in either layer weighted by the opacity of the top layer.

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