Re: [Algorithms] RGB to XYZ conversion

[Sam M. <sam...@ge...>]

>He missed a few signs:
>> [y,Co,Cg]' = [1/4, 1/2, 1/4].[r,g,b]'
>>              [1/2, 0,   -1/2]
>>              [-1/4, 1/2, -1/4]

Yeah, cheers - I was reformatting it from a copied pdf. The signs must
have been eaten somewhere in the process.

> Out of curiosity, what did you mean by "had any issues with it"? YCoCg
> is primarily a replacement for YUV/YCbCr that allows cheaper (and
> lossless) transforms between the two colour spaces and typically does
a
> good job of extracting the correlation in the RGB. If you want to use
it
> for image compression, then it's a good first step.

As other people have commented, I'm also not bothered by the 1-bit
'lossy' precision aspect. That's well below the radar :) 

I'm actually interested in how this luminance+chroma variant stands up
against its equivalents from an art and data 'reduction' point of view.
Can you sensibly work as an artist in YCoCg space? How well does it
represent the rgb correlation in comparison to its alternatives?

I suspect a fair amount of effort went into defining the balance of
luminance/chroma in other variants of this and (at least on the surface)
YCoCg appears to just throw all that away!

Cheers,
Sam