Posted By
Gaia
on 2007-09-18
18:22:16
|  Re: So I want to do plus/4 gfx...
OK, I have reviewed the formulas I have. They were from the infamous 'Pepto' article. Problem is: they are wrong! He talks about Y'UV instead of YPbPr which is the analogue equivalent of YCbCr. When I rebase the color difference signals for YPbPr I get much more consistent hue values and looks more like the real thing.
This means that VICE's palette handling probably isn't good either... it's based on this article (doing YUV) without rebasing to [-0.5;+0.5]. Now I see why Charles Poynton never ceases complaining about the confusion around Y'UV.
I'll probably fix this soon(ish). Another palette change (in RGB mode), yay...
References:
http://en.wikipedia.org/wiki/YCbCr
http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.txt
http://www.pepto.de/projects/colorvic/
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