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I followed this walkthrough on how to select colors with anti-aliasing, and when I finished, everything that hadn't been deleted was not opaque. Yet the layer was at 100% Opacity. How do I fix this??

I want to get rid of the greenish white
I want to get rid of the greenish white

I go into color>color to alpha. and select the greenish white color
I go into color>color to alpha. and select the greenish white color

When I click "ok" the greenish white is gone like i wanted, but the text is opaque, how do I fix this?
When I click "ok" the greenish white is gone like i wanted, but the text is opaque, how do I fix this?

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    Sorry, but this case needs some screenshots, we have no idea what you actually want and what's failed. Explanations with words only are too vague. If you have tried something bizarre, we do not know what it is. – user287001 Jun 7 '19 at 6:29
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    If you are on 2.10, it is possible that you need to add an alpha-channel first (in 2.8 it was added if not there): Layer>Transparency>Add alpha channel. Otherwise, what is not deleted is supposed to stay opaque because deletion is really making things transparent... – xenoid Jun 7 '19 at 8:50
  • There are some images, sorry it took so long – DJChipmunk Jun 10 '19 at 2:57
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    "opaque" means not transparent, "100% opacity" means the same. Can you describe what the images are showing - especially what order they are supposed to be in - and what you'd expect to see instead? – Michael Schumacher Jun 10 '19 at 9:09
  • If you are taking about the checkerboard pattern, this isn't opaque, this is an indication of where the image is transparent (technically, this is a background that you see only where the image is transparent), but it isn't part of the image. – xenoid Jun 10 '19 at 15:34
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  • Fuzzy select the background with the default threshold. Shift-click inside closed areas ('a','e','o') to add them to the selection. In your very specific case (only two constrasting colors in the image), you also do a color selection and use the background color (so yo udon't have to worry about closed areas)

  • Select>Grow by one pixel so that the selection extends over the pixels on the edges of the letters (if the image is dirty (JPEG artifacts), you can grow by 2 or 3px)

  • Colors>Color to alpha and remove the background color. With the selection above, C2A will only apply to edge pixels and leave the core of the letters untouched.
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Color to alpha has affected also partially in the middle of the letters. I guess you have tried to get rid of the remnants of the green color with the treshold sliders in Color to Alpha dialog. After removing the background you have partially transparent letters like these:

enter image description here

How to fix:

GIMP has the curves adjustment as well for RGB channels as for Alpha. Apply Colors > Curves > Alpha and adjust the curve. The right adjustment makes the letters visually opaque, saves the partial transparency of the edges (=anti-aliasing) and it doesn't lift up background:

enter image description here

In my case making the curve steeper did the job. You may need a little S-shaped curve to keep the background invisible.

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