Re: [Gimp-developer] Attempt to summarize the discussion of my examples of what doesn't work in unbounded sRGB

[Teo Mazars <mazarst ensimag grenoble-inp fr>]

----- Mail original -----
> On 04/21/2014 04:47 AM, Teo Mazars wrote:
> > ----- Mail original -----
>
> > > Similar issues are easy to demonstrate with Levels upper and lower
> > > sliders, Gradients, Invert. These really need to be linear light
> > > operations.
> > >
> > > Is there a list of the operations that don't currently use linear
> > > light?
> >
> > Yes, grep for "R'" or "Y'" in the operation directory.
>
> Thanks!
>
> > But... are you really saying that Gradient should be implemented
> > using a non-perceptual color space?
>
> Yes, to be technically correct.
>
> See
> http://ninedegreesbelow.com/gimpgit/gimp-srgb/gradients/gradients.png
>
>
> > I think gradient is a good simple example. How this operation
> > should be implemented exactly?
>
> We want people to be able to draw perceptually linear gradient right?
>
> I completely agree with you that people should be able to draw a
> gradient in a perceptually uniform color space if they want to.
>
> But any such gradient is not technically correct. Colors don't mix
> properly in the almost perceptually uniform regular sRGB color space.
>
> So any color mixing in the regular sRGB color space is technically
> incorrect. For example, you get dark lines at the edges of soft brush
> strokes. The same thing happens with gradients, except the darkening
> artifact is spread out across the gradient and so doesn't look as
> obviously technically incorrect.

Hmm, I understand, then the default black-to-white gradient would be non perceptually linear, which is more 
surprising than the color-to-color gradient. I think I am now convinced this is correct, but it will probably 
be puzzling to use. 

BTW, "gradient" is not such a good example because it's not related to chromaticities, "Invert" would be a 
better one.