Re: Re: associated alpha

On Sat, 5 Feb 2005, Glenn Randers-Pehrson wrote:

> At 11:57 AM 2/5/2005 -0600, Bob Friesenhahn wrote:
>> It would be easy enough to supply the option:
>>
>>   -define tiff:alpha={associated|unassociated|undefined}
>
> Right; I forgot about -define, which is the best way to do it.
>
> In any event, if "-define tiff:alpha" is present then whatever tag is
> in the file is ignored.  The alpha samples don't get changed but
> just the tag telling how to interpret them gets changed.

It may not even be necessary to go this far.  My very latest thinking 
is to simply absorb any existing alpha channel but simply warn if the 
existing alpha channel type is 'undefined' or 'associated'.  If the 
alpha channel is saved, it is either marked as 'unassociated' or an 
image attribute could be used to preserve the original setting.

Unless the alpha channel is used to support rendering or composition, 
GraphicsMagick doesn't really care what it represents.

Bob
======================================
Bob Friesenhahn
[email protected]
http://www.simplesystems.org/users/bfriesen


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