Hello Martin,

On Mon, Nov 10, 2008 at 8:18 AM, Martin Nordholts <[EMAIL PROTECTED]> wrote:
> Hi David
> David Gowers wrote:
>> Ah, so if I want to make the result preserve the alpha of the
>> underlying layer, I'll need to do that via layer mask?
> Exactly, masking should generally be performed *after* blending with the
> new layer mode compositing model.

Cool, I like this, it certainly is more consistent :)

>> FWIW, since you changed the meaning of the layer modes, is this a good
>> time to make compositing gamma-correct?
> Yes definitely. In fact, layer mode compositing with GEGL _does_ work on
> data with gamma = 1.0. That is, the layer mode blending occurs on color
> data in the babl format "RaGaBaA float", i.e pre-multiplied, linear
> light 32 bit per channel RGBA.
> The reason you don't see a difference when toggling Use GEGL is that now
> during development the source data, namely the data from the tiles of
> the TileManagers of the GimpDrawables, are treated as if containing
> color data in the babl format "RGBA u8", i.e. linear light 8 bit per
> channel RGBA. A more correct assumption would be "R'G'B'A u8", i.e.
Thank you for explaining that, it was just what I suspected :)

I'll see what happens when I make that change :)
(apparently just one line, app/core/gimpprojection.c:391, is needed to
be changed to implement this now :D)

> gamma corrected RGBA.
> The long term goal is of course to make sure color space conversions are
> correct throughout the whole image processing pipeline, taking into
> account the current color profile of the image etc.

So eventually we need to be able to construct on-demand babl_formats
which utilize arbitrary profiles, and  have babl depend on lcms to get
a acceptably quick transform between those and the standard spaces?
And recognize the use of standard colorspace profiles (eg sRGB,
linear-light RGB) so we can get faster processing for them?


Reticience and self-censorship is a farce.  The deceiver does not
himself know the truth, anything that he holds back he holds back not
only from others but from himself. Fuck censorship. "I yam what I
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