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Colorkeying using the alpha channel: How to make the alpha channel?

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Yes, this is another of those "how do i get colorkeying in OpenGL" questions. Luckily i have already figured out this can be done using the alpha channel(you see, i actually read all the other posts . My problem is how to create the alpha channel easily. It would be fairly easy to make a little command line utility that walked through a TGA image with an alpha channel(all the loading could be handled by DevIL which im using anyway), and set the alpha values based on the value in the other channels. But i just cant imagine that there isnt a program that can auto-set the alpha channel so that its 255 for all pixels with color != some_rgb_value, and 0 where it is == some_rgb_value, it seems so useful, and so simple. So any ideas? Can it be done with one of the standard image editing programs(Paint Shop/Photoshop/GIMP)? [edited by - ziphnor on July 30, 2002 8:17:49 AM]

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