On Wed, Jun 13, 2012 at 10:03 AM, Larry Gritz <[email protected]> wrote:

> (Exercise for the reader: under what circumstances, and for which formats,
> could you be SURE that a 4-channel image did not contain an alpha?)
>

A CMYK TIFF image?

That's clearly a corner case, but I guess if I had two cmyk tiff images and
tried to "over" them I would be sad if the tool ignored the TIFF reader
saying "no alpha" and just assumed "K" was alpha. I don't think that's
worth worrying about, but I just wanted to do the "exercise". :) I think
there are CMYKA tiff images out there.

It would probably be more commonly annoying if a reader didn't want to
assume channel 3 was alpha, but it was and I just wanted the over to work
with what is obviously (to me) RGBA images.

Maybe it's better if the readers are more aggressive in identifying a alpha
channel unless they are sure it's not?

--jono
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