2002.03.06 22:32 "RE: Photoshop Alpha Channel", by Chris Cox

Chris, I apologise if the wording caused offence.

No, just puzzlement.

I think this partly answers my question so a more specific one is now what is the simplest way to change an existing channel from type 1 (associated) to type 0 (unspecified) so I can access it from the Photoshop channels palette.

You can copy the transparency to another channel using the calculations command.

But you can't easily replace the image transparency without damaging the image contents.

So the easiest way would be a quick program that changes all the extra channels in a TIFF file to 0. Yyou don't even have to parse the full file or use libtiff - just parse enough of the structure to find the extra channels tag, change that in place and stop.

Where are you getting files with incorrectly marked channels?

P.S. to those who have complained about my signature I'm sorry but I have absolutely no control over this as it is added on the way out through the companies firewall.

Please notify your system administrator that they're a taco short of a combination platter.

Even the most anal of law firms I work with doesn't have a sig that big.

Chris