Re: Which one has the right color, Emacs or GIMP?

[Miles Bader]

"Stephen J. Turnbull" <address@hidden> writes:
>  > Huh?  RGBA is just a notation for a storage format, it says nothing
>  > about how the components should or should-not-be interpreted.
>
> Of course it says something.  It says that the various components red,
> green, and blue shall be used in strengths given as a fraction of
> their maximum, as modified by the alpha if the display is capable.
>
> It's possible to quibble about whether that "strength" must be linear
> or merely increasing (the latter interpretation admits gamma
> adjustment among others).  But to say "it says nothing" is too much of
> a stretch.

Er, sure as a vague "the components have a positive correlation with the
redness, greenness, and blueness of the resulting color the user sees"
notion, sure, there's some information there. :)

I'm sure there's some at least _somewhat_ more precise definition
(linear/exponential/whatever, though I suspect not much more) for things
sent to the X server and stored in rgb.txt.

> IMHO, Emacs should delegate this to either the display hardware and
> drivers

Sadly, they're usually all fucked up too though.

In general, Emacs _can't_ really just ignore the issue unless it's
merely acting as a middleman exchanging colors amongst components which
are known to be in agreement about their interpretation.  Since Emacs is
_not_ just doing that -- it also reads image files using a variety of
libraries which may not have compatible interpretations for the values
they yield, and [pertinently to this thread] uses color numbers from the
user.  Since the latter are presumably intended to be at least somewhat
platform independent, and different platforms can have wildly different
display systems, we then have to worry about the issue for those.

-Miles

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