On 30.09.2010 05:39, bobdobbs wrote:
> Hi all.
> I'd like to delete in such a way that transparency remains.
> I've found that this is the default when I'm working on images that I've 
> created myself.
> But if I'm working on an image that I've downloaded or gotten from another 
> source, I can't predict the behaviour of functions that remove pixels.
> In my immediate case, I've got a icon with a white background. I want to 
> remove the background.
> However, when I try to remove the white pixels, the result is black pixels.
> How can I figure out what the result of deletion operations on pixels will be?
> How can I consistantly remove colour, leaving transparency?

short answer: always add an alpha channel to the layer, either using the layers 
or via Layers->Transparency->Add Alpha Channel [1].

The alpha channel determines the transparency for each pixel. The absence of an 
alpha channel
means that all pixels are fully opaque and hence they get deleted to background 
color [2].


[1] http://docs.gimp.org/2.6/en/gimp-layer-alpha-add.html
[2] http://docs.gimp.org/2.6/en/gimp-image-combining.html#gimp-layer-properties
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