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


From: Michael Heerdegen
Subject: bug#25890: `color-values` gives wrong value
Date: Wed, 01 Mar 2017 00:42:02 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux)

Eli Zaretskii <address@hidden> writes:

> 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.)
>
>
> --- lisp/color.el~0   2017-01-02 06:25:09.000000000 +0200
> +++ lisp/color.el     2017-02-28 17:35:43.570586100 +0200
> @@ -52,14 +52,14 @@
>  If FRAME cannot display COLOR, return nil."
>    ;; `colors-values' maximum value is either 65535 or 65280 depending on the
>    ;; display system.  So we use a white conversion to get the max value.
> -  (let ((valmax (float (car (color-values "#ffffff")))))
> +  (let ((valmax (float (car (color-values "#ffffffffffff")))))
>      (mapcar (lambda (x) (/ x valmax)) (color-values color frame))))
>  
>  (defun color-rgb-to-hex  (red green blue)
>    "Return hexadecimal notation for the color RED GREEN BLUE.
>  RED, GREEN, and BLUE should be numbers between 0.0 and 1.0, inclusive."
> -  (format "#%02x%02x%02x"
> -          (* red 255) (* green 255) (* blue 255)))
> +  (format "#%04x%04x%04x"
> +          (* red 65535) (* green 65535) (* blue 65535)))
>  
>  (defun color-complement (color-name)
>    "Return the color that is the complement of COLOR-NAME.

With that patch, for me in the recipe of bug #24273, it makes a
difference; now

(color-name-to-rgb "#ffffff")
==>
(0.9961089494163424 0.9961089494163424 0.9961089494163424)

and

(color-name-to-rgb "white")
==>
(1.0 1.0 1.0)


For the recipe of this bug report, the values are the same as without
the patch.

I guess this is what you expected.  But is it ok that "#ffffff" is not
equivalent to "white"?  If it is, seems there is no inconsistency left.


Thanks so far,

Michael.





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