I don't have a good way to explain this just using words, so here's a partial screenshot:

Weird selection result

Even when I set the threshold to 0, Fuzzy Select is grabbing a disproportionately large portion of an image. In the screenshot, I'm trying to only grab the darkest color. It's almost like there's an after-image stuck in the tool's settings. There's only one layer (with no layer mask) in the xcf, so it's not an issue of having the wrong layer selected.

Am I just flat-out doing something wrong? I tried messing with all of the other tool options, but haven't had luck.

2 Answers 2


Because it selects by color, and the difference between the black area and the near-black area is not color but opacity (you can use the Pointer dialog to check this). To achieve what you want:

  • Layer>Transparency>Alpha to selection to generate a selection based on transparency
  • Select>Selection editor to open the selection editor. You will get a "negative" of your image (white is what is fully selected, and the "Alpha to selection" selects pixels according to their opacity).
  • Click on the white part (this acts as a "Select by color" on the selection values) and this should restrict your selection to the fully opaque bits.

Alternative method:

  • Layer>Transparency>Alpha to selection to generate a selection base don transparency
  • Select>Save to channel to save the selection. At that point the saved channel is the "active drawable" and so the Paint tools will act on it.
  • Use the Threshold tool to remove the gray band.
  • In the Channels list, right click and Channel to selection to make a selection from the result.

I think the problem is because you have different areas of transparency - but the Fuzzy select tool works by comparing differences in colour.

Here's a workaround that might solve it for you.

  1. Create a white background layer below the image layer/s, and enable its visibility.
  2. Set the fuzzy select tool options to Select by: Composite and Sample Merged
  3. Try to make your selection again.
  4. When you have finished, you can hide the background layer visibility, or just delete it.
  • 1
    Select by Composite just selects using RGB. Your solution works if you use "Sample merged".
    – xenoid
    Jun 8, 2017 at 12:25
  • @xenoid You are absolutely correct, I missed that out!!. Edited my answer. Thanks for that.
    – Billy Kerr
    Jun 8, 2017 at 18:10

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