I have a strange behavior, I'm using GIMP 2.10.8 on Ubuntu 18.10, Sorry I'm newbie.

  1. I copied one image and pasted to new layer.
  2. I changed the color using Colors -> Colorize
  3. I wanted to increase brightness so did the following Colors -> Brightness/Contrast increased Contrast to 70+
  4. Preview working fine, when I hit OK, it's not applying.

enter image description here

  • Hi. Welcome to GDSE. I've tried to repeat what you did, but it works as expected, and I can't replicate the problem you are experiencing. Can you check your image mode is in RGB mode, and not Indexed mode. It's the only thing I can think of.
    – Billy Kerr
    Commented Jan 13, 2019 at 18:53

1 Answer 1


You can have such a problem if your layer has a partial opacity (ie, Alpha<100% on all pixels). When you apply Brightness-Contrast, you are viewing a fully opaque preview, but when you commit, alpha is restored and this dims the effect.

This could be a bug in Gimp 2.10

  • I agree. That seems to be the problem. I tried again to replicate the issue demonstrated by the OP, but this time I used an image with semi-transparent pixels. It would seem to be a preview issue/bug more than anything else, the filter still works. It just looks different when you commit.
    – Billy Kerr
    Commented Jan 13, 2019 at 22:16

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