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Old 4th October 2015, 14:04   #18  |  Link
feisty2
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Join Date: Oct 2012
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Quote:
Originally Posted by colours View Post
It's vaguely ironic to see feisty2 post about "mathematical precision" and using Dither tools to illustrate that, when Dither tools has off-by-one errors scattered throughout the full-range colour conversion functions.
there's no such thing as infinite precision for computers, I don't see any other better option to do it, anyways, I'll explain what I was saying with the following

Quote:
Originally Posted by colours View Post
Also, good job missing vivan's point. How surprising it is that you find the argument "pointless" when you just ignore what everyone else says.
I get that stuff vivan or you stated

suppose:
1. there was infinite precision for computers
2. all rgb-yuv444-rgb stuff was done correctly under infinite precision
3. the input value was 0.123

the output value of both "ycgco" and "ycbcr" should be 0.123000000... or 0.1229999999... both are mathematically equal to 0.123, the input value
perfect, end of the story

now the reality is, there's no infinite precision, only higher but still finite precision

say, the higher precision here is "6 significant figures"
the output of ycgco would be like, 0.123000, still mathematically equals to 0.123, cuz there're only things like /2 and /4 inside ycgco stuff, and they won't produce infinite decimals long as the input is not infinite precision

the ycbcr output might be like 0.123456, which != 0.123, cuz obviously ycbcr requires infinite precision for intermediate values to stay the zero error status, some intermediate value gets truncated to 6 significant figures and that leads to the error presented in the output value

the disagreement starts right from here

you and vivan think 0.123456 will become 0.123 if rounded down to 3-significant-figure precision and will =0.123 again so it's lossless

and I think it's cheating, the mathematically lossless method should have an output like ycgco, lossless without rounding

Last edited by feisty2; 4th October 2015 at 14:18.
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