bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Simen Heggestøyl]

The docstring for `color-name-to-rgb' states the following:

"Normally the return value is a list of three floating-point numbers,
(RED GREEN BLUE), each between 0.0 and 1.0 inclusive."

When passing the hex value for white the return value is as expected:

     (color-name-to-rgb "#ffffff")
          ⇒ (1.0 1.0 1.0)

But when passing the name of the same color, the return value becomes
different:

     (color-name-to-rgb "white")
          ⇒ (1.00390625 1.00390625 1.00390625)


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bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Julien Danjou]

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On Sat, Aug 20 2016, Simen Heggestøyl wrote:

> The docstring for `color-name-to-rgb' states the following:
>
> "Normally the return value is a list of three floating-point numbers,
> (RED GREEN BLUE), each between 0.0 and 1.0 inclusive."
>
> When passing the hex value for white the return value is as expected:
>
>      (color-name-to-rgb "#ffffff")
>           ⇒ (1.0 1.0 1.0)
>
> But when passing the name of the same color, the return value becomes
> different:
>
>      (color-name-to-rgb "white")
>           ⇒ (1.00390625 1.00390625 1.00390625)

What are the return values of:
 (color-values "white")
and
 (color-values "#ffffff")
?

-- 
Julien Danjou
/* Free Software hacker
   https://julien.danjou.info */

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bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Simen Heggestøyl]

On Sat, Aug 20, 2016 at 12:06 PM, Julien Danjou <julien@danjou.info> 
wrote:
> What are the return values of:
>  (color-values "white")
> and
>  (color-values "#ffffff")
> ?

(color-values "white")
     ⇒ (65535 65535 65535)

(color-values "#ffffff")
     ⇒ (65280 65280 65280)

-- Simen

bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Eli Zaretskii]

> Date: Sat, 20 Aug 2016 12:11:46 +0200
> From: Simen Heggestøyl <simenheg@gmail.com>
> Cc: 24273@debbugs.gnu.org
> 
> On Sat, Aug 20, 2016 at 12:06 PM, Julien Danjou <julien@danjou.info> 
> wrote:
> > What are the return values of:
> >  (color-values "white")
> > and
> >  (color-values "#ffffff")
> > ?
> 
> (color-values "white")
>      ⇒ (65535 65535 65535)
> 
> (color-values "#ffffff")
>      ⇒ (65280 65280 65280)

Which means "white" and "#ffffff" are not the same color.

bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Andreas Schwab]

On Aug 20 2016, Eli Zaretskii <eliz@gnu.org> wrote:

>> Date: Sat, 20 Aug 2016 12:11:46 +0200
>> From: Simen Heggestøyl <simenheg@gmail.com>
>> Cc: 24273@debbugs.gnu.org
>> 
>> On Sat, Aug 20, 2016 at 12:06 PM, Julien Danjou <julien@danjou.info> 
>> wrote:
>> > What are the return values of:
>> >  (color-values "white")
>> > and
>> >  (color-values "#ffffff")
>> > ?
>> 
>> (color-values "white")
>>      ⇒ (65535 65535 65535)
>> 
>> (color-values "#ffffff")
>>      ⇒ (65280 65280 65280)
>
> Which means "white" and "#ffffff" are not the same color.

Actually they are, because #ffffff and #ffffffffffff are the same color
on a display with 8 bits per color.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Eli Zaretskii]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: Simen Heggestøyl <simenheg@gmail.com>,
>   julien@danjou.info,  24273@debbugs.gnu.org
> Date: Sat, 20 Aug 2016 14:07:08 +0200
> 
> On Aug 20 2016, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> >> Date: Sat, 20 Aug 2016 12:11:46 +0200
> >> From: Simen Heggestøyl <simenheg@gmail.com>
> >> Cc: 24273@debbugs.gnu.org
> >> 
> >> On Sat, Aug 20, 2016 at 12:06 PM, Julien Danjou <julien@danjou.info> 
> >> wrote:
> >> > What are the return values of:
> >> >  (color-values "white")
> >> > and
> >> >  (color-values "#ffffff")
> >> > ?
> >> 
> >> (color-values "white")
> >>      ⇒ (65535 65535 65535)
> >> 
> >> (color-values "#ffffff")
> >>      ⇒ (65280 65280 65280)
> >
> > Which means "white" and "#ffffff" are not the same color.
> 
> Actually they are, because #ffffff and #ffffffffffff are the same color
> on a display with 8 bits per color.

I don't think I follow you.  What does 8 bits per color have to do
with this, and how do you know the OP has 8 bits per color on his
display?

FWIW, on my display, I get (65535 65535 65535) for both expressions.

bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Julien Danjou]

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On Sat, Aug 20 2016, Eli Zaretskii wrote:

> I don't think I follow you.  What does 8 bits per color have to do
> with this, and how do you know the OP has 8 bits per color on his
> display?
>
> FWIW, on my display, I get (65535 65535 65535) for both expressions.

I get (65280 65280 65280) for both on my display.

The problem is that `color-name-to-rgb' expect to find the brightest
point by calling (color-values "#ffffff") whereas it seems in this case
it's less bright than "white". Is that something possible?

What kind of system are you running Simen?

-- 
Julien Danjou
;; Free Software hacker
;; https://julien.danjou.info

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bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Andreas Schwab]

On Aug 20 2016, Eli Zaretskii <eliz@gnu.org> wrote:

> I don't think I follow you.  What does 8 bits per color have to do
> with this,

Only the upper 8 bits are significant.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#24273: 25.1.50; Unexpected return value from `color-name-to-rgb'

[Simen Heggestøyl]

On Sat, Aug 20, 2016 at 2:32 PM, Julien Danjou <julien@danjou.info> 
wrote:
> I get (65280 65280 65280) for both on my display.
> 
> The problem is that `color-name-to-rgb' expect to find the brightest
> point by calling (color-values "#ffffff") whereas it seems in this 
> case
> it's less bright than "white". Is that something possible?
> 
> What kind of system are you running Simen?

I'm running Debian (testing).

-- Simen