Re: [Gimp-developer] [Gimp-user] Time to fork BABL and GEGL

[Simon Budig <simon budig de>]

Hi Elle.

Elle Stone (ellestone ninedegreesbelow com) wrote:
> Whether to *ever* use unbounded sRGB chromaticities to perform edits on
> UserRGB data is NOT AN IMPLEMENTATION DETAIL.
>
> Unbounded sRGB is a mistake, pure and simple, *unless* the data is intended
> by the USER to be HDR sRGB data.

It really is not about editing. Even when for some reason the data in
the graph is present as unbounded sRGB data the multiplication op will
request the data as userRGB which will result in a transform, the op
will get the colors in the desired space.

> In case you don't understand this, HDR sRGB data is still *bounded* by the
> sRGB xy chromaticities. It's only unbounded along the Y axis. There are NO
> negative channel values in HDR sRGB data unless the *user* chooses to do
> something odd, in which case the *user* is responsible for fixing the
> results.

I think you are missing that "unbounded" also allows *negative* R, G or B
coordinates. That makes the colors imaginary in the sRGB color space,
but it still is possible to convert them to all other RGB color spaces.

Unbounded sRGB can express all the colors XYZ can express.
Transformations from userRGB to sRGB to userRGB are lossless.

Bye,
        Simon

-- 
              simon budig de              http://simon.budig.de/