Re: [Gimp-developer] Overlay Mode - fix.

On Fri, Nov 16, 2012 at 8:33 PM, Elle Stone <l elle stone gmail com> wrote:
> Hi all,
> A couple different lines of discussion are in this thread, the correct
> way to implement Overlay in regular sRGB, the effect of linear gamma
> blending with respect to changing w3 standards, how to deal with
> legacy blend modes after the switch to linear light image editing.
> …
> It seems to me that instead of "50% gray" a more reasonable inflection
> point for the overlay mode in digital image editing (at least in
> linear light) would be Lab (50,0,0) to preserve the effect of
> stretching midtones and compressing shadows and highlights. I suspect
> the formulas for Multiply and Screen could use some tweaking, too, to
> accomodate linear light blending.

Critically evaluating what is the reasonable color space to use for
various operations is indeed something that we need to do. For many
operations - like blurs, various warps and transforms linear makes
most sense. And for operations that will work better in a more
perceptual space I think as Elle states here - that using CIE Lab (or
something very similar) is likely to be a better choice than sticking
with sRGB gamma curves for the non-linearity.

/Øyvind K.
«The future is already here. It's just not very evenly distributed»
                                                 -- William Gibson                  

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