Re: [csswg-drafts] [css-color-4] Do gradients/animations using lab/lch colors interpolate in the Lab colorspace? (#4647)

. Saying that

> Nothing is done in linear RGB except when the user specifically asks for it, as they might when the output level is used as a mask. Blur and other filters are straightforward alpha composition in sRGB or linear RGB, as the user chooses.

without seeing the major bug and a fundamental design mistake it is, is why you get 

>  your apparent inability to convey your ideas without inexplicably calling someone an idiot in the process

There is literaly zero polite way to describe the clusterfuck in this thread. https://github.com/w3c/csswg-drafts/issues/4647#issuecomment-571537439 is one of the most self-explanatory one. How is a gradient from green to red skewing to a large orange part better than the "RGB" labelled one (what RGB by the way ?).

Image processing is light transport all the way. Color happens in your brain, no need to bother about it if you are not inside a CMS doing chromatic adaptation and such. Light is well known and well modelled by light. None of the light physics involves "perceptual" cubic roots functions.

The only part where I use Luv space in my software is for controls in GUI. Then Luv parameters are converted to Yuv -> Yxy -> XYZ -> RGB, and the pixel processing happens in RGB.

What really makes me rage here, is the problems caused by image operations in Lab/name-your-perceptual-mess are well known in a universe of retouchers and CGI artists that seems entirely parallel to yours.

Alpha composition is not alpha composition in sRGB. Alpha means occlusion. Occlusion is an optical thing. Optics don't care about your OETF. No CGI artist in his right mind would overlay CGI on top of real footage in any space with a non-linear OETF. That simply doesn't work.


-- 
GitHub Notification of comment by aurelienpierre
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4647#issuecomment-634578211 using your GitHub account

Received on Wednesday, 27 May 2020 10:41:59 UTC