What coefficients does Krita use for YUV/YCbCr?

[Matthew Woehlke]

Cyrille Berger wrote:
> Hi
> 
> On Wednesday 23 May 2007, Matthew Woehlke wrote:
>> I don't know if anyone follows k-c-d, but I'm working on a color
>> blending function for kdelibs that will support HSY color space (like
>> HSL but with luma as in YUV/YCbCr color spaces). Alas, there are two
>> common sets of coefficients used to calculate Y:
>>
>> 601: Y' = 0.299  R' + 0.587  G' + 0.114  B'
>> 709: Y' = 0.2126 R' + 0.7152 G' + 0.0722 B'
>>
>> I figure this is probably the best place to ask; which would be better
>> to use in kdelibs (or should I offer /both/)? Which does Krita use?
> 
> Krita 1.6 is hard coded to use 601. While for 2.0 the plan is to allow use any 
> coefficients, even non common :)
> 
> 601 coefficients are the default for TIFF. I guess that for your use any of 
> the coeffcients are good enought anyway.

Ok, it sounds like 601 is fairly common in "traditional" digital imaging 
(even though wikipedia talks about 709 everywhere with only a footnote 
to 601). Thanks!

Hmm, I guess if I /really/ wanted to be clever I would use 
user-configurable coefficients so that HSY would actually correctly 
match the user's display. Heh, wouldn't /that/ be sweet. :-)

...Maybe for KDE 5 ;-).

-- 
Matthew
"I can hear you / just barely hear you / I can just barely hear you"
   -- "I Can Hear You", by They Might Be Giants