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I have a 2D logo. I want to create an alpha channel around the base image. I have tried all manner of combinations of inverting selection, etc., but cannot get GIMP to just fill the blank space with alpha channel. Do I really need to do this manually pixel by pixel with the eraser tool ?
(Aug 31, 2014 17:58)WhyDoIHaveToCreateAnAccount Wrote: [ -> ]I have a 2D logo. I want to create an alpha channel around the base image. I have tried all manner of combinations of inverting selection, etc., but cannot get GIMP to just fill the blank space with alpha channel. Do I really need to do this manually pixel by pixel with the eraser tool ?

You have to create an account in order to contribute (in your case post) to the forum. This is not UseNet. Believe me, it is a lot easier here than on other forums

Back to the question. Depends on the logo.

Does your image have an alpha channel to start with?
Gimp menu Layer -> Transparency -> Add Alpha Channel
If that is grayed-out there is one. Then with a selection Edit -> Cut should remove something. If the wrong part invert the selection.

If the logo has a single colour background then a simple color-to-alpha should work Gimp menu Colors -> Color To Alpha.
see: http://docs.gimp.org/2.8/en/plug-in-colortoalpha.html

Or make a selection using one of the selection tools and apply some principles. see: http://gimpforums.com/thread-proper-subj...-painting?

If the background is complicated then sometimes a layer mask is the way to go see: http://docs.gimp.org/2.8/en/gimp-layer-mask-menu.html and subsequent pages.

If your logo is not too controversial and you have worked through the above to no avail, then post it to get further advice.
The first thing to do is to make sure your layer has an alpha channel.
Layer > Transparency > Add alpha channel
(Or you can do it the Layers window. Right click the layer and select Add Alpha Channel. The layer name is in bold if it does not have an alpha channel.)

Now make your selection. Invert the selection if necessary.
Now do Edit > Clear
(or press the Delete key)
Cheers, TY for the assistance. Sorry for my tone. I was rather frustrated.
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