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#41544
26.3; Possible incorrect results from color-distance
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Message #46 received at 41544 <at> debbugs.gnu.org (full text, mbox):
1 juni 2020 kl. 19.44 skrev Eli Zaretskii <eliz <at> gnu.org>:
>> I'm just looking at the changes. I see a change in how colors are
>> converted to RGB triplets. I see a change in what colors are
>> considered dark and light, with a new function which decides that that
>> is being used for frame background mode and in several lisp/term/
>> files, including 16-color terminals. I'm asking why do we want to
>> make all those changes, which modify very basic aspects of our color
>> support on many terminals.
>
> And then, of course, there are the changes in color-distance itself,
> which change the values it returns. Again, why such significant
> changes to fix an otherwise insignificant bug?
It is difficult to give precise answers to vague complaints. Take one thing at a time: as I wrote, there are two different patches addressing two almost completely different issues. Let's start with the color-distance changes, out of respect for the bug reporter if nothing else.
It is not possible to change a function without changing it. Either we fix it or we don't. The reported bug was about broken symmetry, which is rather embarrassing; as written previously, the first analysis uncovered deeper issues worth fixing, such as loss of precision and (especially) the nonlinearity that causes triangle inequality violation.
The proposed fixes to color-distance, I hope you agree, are straightforward, reasonable and address all these points. Callers have been updated with carefully recomputed comparison constants; I detailed how they were obtained in a previous reply, and test have all been satisfactory.
This bug report was last modified 4 years and 304 days ago.
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