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[Openexr-devel] On YUV support
From: |
Billy Biggs |
Subject: |
[Openexr-devel] On YUV support |
Date: |
Fri, 28 Nov 2003 13:52:34 -0600 |
User-agent: |
Mutt/1.5.4i |
The website has some notes on YUV support in OpenEXR and asks for
suggestions. I would like to offer some.
EXR files currently store linear intensity values for RGB. However,
the YUV used in video systems is always based on gamma corrected RGB:
the Y in a YUV system is not really luminance [1]. Because of this, I
do not see any way to convert from linear intensity RGB to the U, V
channels of a video system without clamping to [0,1], making the use of
EXR over a 16-bit per channel integer format like PNG seem useless.
Because of this, I would recommend dropping the idea of a YUV mode,
and the channel names U and V, until a better defined use case is found.
I do have an alternate suggestion for some more channel names in EXR
files. Specifying colours as CIEXYZ triples is quite useful, and I
would recommend "X" and "Z" as channel names. I would then recommend
changing this text:
Y luminance, used either alone, for gray-scale images, or in
combination with U and V for color images.
to this:
Y luminance, used either alone, for gray-scale images, or in
combination with X and Z for color images in CIEXYZ.
Which makes much more sense and seems a lot more useful.
Thoughts?
-Billy
[1] http://www.poynton.com/PDFs/YUV_and_luminance_harmful.pdf
- [Openexr-devel] On YUV support,
Billy Biggs <=