I'm foolish.
I should have realised this.

Thank you.

>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 dialog
>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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