RE: Re: associated alpha

On 2/11/05 Glenn Randers-Pehrson wrote:

> At 05:13 PM 2/11/2005 -0600, Bob Friesenhahn wrote:

>>The only question is 
>>if it is ok to automatically promote a colormapped image to TrueColor 
>>type when it is saved.

> There may be filesize implications.  I don't know about TIFF but an
> indexed-color PNG is generally about half the size of the equivalent
> 24-bit RGB.

> Glenn

I've heard of indexed color TIFFs used for game sprites because of
the file size reduction. File size seems like a primary reason why
someone would use them.

I'm not the right person to comment since I haven't used colormapped
TIFFs with alpha, but I think the lesser evil would be, by default, to
promote the image to TrueColor, pre-multiply, and color reduce again.

David




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