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bug#25890: `color-values` gives wrong value


From: Rasmus
Subject: bug#25890: `color-values` gives wrong value
Date: Wed, 01 Mar 2017 10:55:22 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux)

Hi,

Eli Zaretskii <address@hidden> writes:

> I think there's a bug in color.el: it assumes that the #RGB notation
> uses 24 bits, i.e. each component maxes out at 255.  But Emacs does
> its color calculations based on 16-bit components, which max out at
> 65535, which is why #ffffff does NOT produce (65535 65535 65535), the
> white color.  (We decided long ago to use 16-bit components because X
> APIs such as XParseColor on some systems, including yours, work with
> such components.)  IOW, #ffffff is parsed as #ff00ff00ff00, and that
> is not "white".
>
> So I think the patch below is what is needed to fix this problem.  Can
> you try it?  (There's one user of the functions the patch changes,
> shr-color.el, which will need to be adapted to the change, if we
> decide to install it.)

The test I used before now works for me:

    (set-frame-parameter (selected-frame) 'background-color
                         (color-darken-name "light yellow" 5))

Other noteworthy effects of the change were already addressed by Michael.

Thanks,
Rasmus

-- 
Hvor meget poesi tror De kommer ud af et glas isvand?






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