Fixed painting on transparent layers

Leonard Rosenthol leonardr at
Sun Jan 25 18:19:54 CET 2004

At 4:47 PM +0100 1/25/04, Boudewijn Rempt wrote:
>Thanks -- I've checked out GM and done a diff of composite.c. I think
>that it has most of what I need at the moment. One thing I still don't
>quite get. I had supposed that you'd need different composition algorithms
>for different colour models, but I cannot find them, even though I have
>found support for CMYK in GM/IM.
	IM/GM do support CMYK data for images, but not all operations 
are supported in CMYK mode - for example, I think compositing is one 
of them :(.  I believe the IM/GM will convert to RGB before 
performing a composite...(but you should probably check the code).

	However, do you need a different algorithm for compositing in 
different color models - to some extent, yes, but not for most 
things.  Simple compositing should work the same regardless of model 
- but when you get into unusual modes (any that require doing the 
operation in HSB, for example), then yes, you need to treat CMYK 
different from RGB.

Leonard Rosenthol                            <mailto:leonardr at>

More information about the kimageshop mailing list