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List: kde-kimageshop
Subject: Re: What coefficients does Krita use for YUV/YCbCr?
From: Matthew Woehlke <mw_triad () users ! sourceforge ! net>
Date: 2007-05-23 21:22:46
Message-ID: f32bb6$kgb$1 () sea ! gmane ! org
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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
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