actually they must be saved in .png far as i know, any attempt to open a PhotoShop document(.psd) using quicktime tech will result in message stating similar "you need photoshop to view/edit this file" this will be in place of the actual document, followed by the same translated into several languages.
so then any image format that supports alpha channels is basically saying it supports transparencies. wth........
not really, you can save multiple formats with an alpha channel...that don't necessarily support them;
GIFs which support transparency can have an alpha channel as well, but you won't be able to view them...only browsers that can are IE mac edition, and iCab.
picts can have an alpha channel, it will permutate the colors in the image,red becomes yellow, white becomes blue...as such white will not be white and therefroe you forfeit transparency.
the alpha channel as far as PhotoShop is concerned is just a good way to permanenetly save multiple selections/masks within qa single file...ie if you were doing a gradual dissolve effect you could mask out the areas instead of creating a multitude of layers, which because of them being greyscale are in general much smaller.(load selection/save selection)
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