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up vote 3 down vote favorite

I have a layer that is at 50% opacity. But in certain regions, I want to use a paintbrush to bring the opacity higher. How can I do this?

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Welcome, Hunter! Typically we want questions here to be specifically related to photography, not just image editing; if your question is photography-related, perhaps you could edit it a bit to clarify that relevance? – Reid Dec 25 '10 at 2:12
@Reid: Am I mistaken to think that this site is called "Photography & Photographic Editing"? Sure, we don't know for certain that what this person is editing is a photograph, but certainly the gimp is a tool that is used for Photographic Editing. I don't see why this deserves a down-vote. – lindes Dec 25 '10 at 5:16
There is a graphics site that will start in 2011 as part of area51 – hunterp Dec 25 '10 at 6:38
Welcome to Photo.SE. As Reid stated, we to prefer to keep the questions here on-topic. If your question is specifically related to photography, could you edit it to clarify exactly what you are doing? There may be a better way to achieve what you are trying to do. If your question is not related to photography, but is about general image editing, we'll need to close it, as it would fall in the off-topic category. Thanks! – jrista♦ Dec 26 '10 at 6:30
@lindes, see discussion in meta and feel free to contribute. – Reid Dec 26 '10 at 20:40

closed as off topic by Itai, ahockley, Reid, jrista♦ Dec 27 '10 at 2:09

Questions on Photography Stack Exchange are expected to relate to photography within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.

2 Answers

up vote 1 down vote accepted
  1. Set opacity to 100%.
  2. Add layer mask.
  3. Fill the mask with 50% gray.
  4. Draw into mask using black and white any way you want.
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up vote 2 down vote

I may be wrong, but I don't think that what you are looking for is feasible. The layer opacity is called that because it applies to the whole layer, and the only thing you can do is make part of the layer more transparent by increasing alpha, not less.

If you want to modulate higher, then you must select either 100% opacity for that layer (probably the easiest option) or the maximum opacity you intend to use and make most of your image partially transparent with the alpha channel to reach the 50% you want in most places.

On this layer you then check the layer menu to add a mask (and transfer the existing alpha channel if there is one, such as after you have gone through this process once). When you paint in the mask, black makes the painted portion of this layer totally opaque, while white makes it totally transparent. Choose your tools to put the right shade of grey where you want and it'll give you exactly the alpha channel that you want. When done, go to the layer menu again, mask -> apply the mask. You're done.

I think this would give you the type of control you want.

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Yeah, i've been using gimp's black/white opacity mask – hunterp Dec 25 '10 at 4:31

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