about pictures with alpha component!

Hi there,

I find some pictures i load as texture have a transparent background, how to make these pictures?

Could i read a picture file to the memory, then add the alpha component for the color to be transparent,
then save it back to the file? or any software can do this?

thanks a lot!

http://docs.gimp.org/nl/gimp-layer-alpha-add.html

paint.net in Windows
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Need .NET framework