"Eli Zaretskii" <[EMAIL PROTECTED]> writes:
>> From: Dan Nicolaescu <[EMAIL PROTECTED]>
>> Date: Wed, 06 Apr 2005 01:17:11 -0700
>>
>> This comment in tty-colors.el:tty-color-standard-values
>>
>> ;; Translate the string "#XXYYZZ" into a list
>> ;; of numbers (XX YY ZZ). If the primary colors
>> ;; are specified with less than 4 hex digits,
>> ;; the used digits represent the most significant
>> ;; bits of the value (e.g. #XYZ = #X000Y000Z000).
>>
>> does not seem to match the way the `color-name-rgb-alist' seem to have
>> been created from the values in rgb.txt.
>> A random example:
>> >From color-name-rgb-alist:
>> ("lavenderblush" 65535 61680 62965)
>> ^^^^ ^^^^ ^^^^
>> 0xffff 0xf0f0 0xf5f5
>>
>> >From rgb.txt: lavender blush 255 240 245
>> 0xff 0xf0 0xf5
>> So the 8 to 16 bit conversion seems use the same byte value for both
>> the high and low byte value.
>
> The comment you cited reflects what I found in the X documentation.
> Here, for example, is an excerpt from the X(7) man page on a Debian
> GNU/Linux box (fencepost.gnu.org):
>
> For backward compatibility, an older syntax for RGB Device
> is supported, but its continued use is not encouraged.
> The syntax is an initial sharp sign character followed by
> a numeric specification, in one of the following formats:
>
> #RGB (4 bits each)
> #RRGGBB (8 bits each)
> #RRRGGGBBB (12 bits each)
> #RRRRGGGGBBBB (16 bits each)
>
> The R, G, and B represent single hexadecimal digits. When
> fewer than 16 bits each are specified, they represent the
> most-significant bits of the value (unlike the "rgb:" syn-
> tax, in which values are scaled). For example, #3a7 is
> the same as #3000a0007000.
>
> So I think the code in tty-colors.el is correct in this matter. It
> is, however, possible that the RGB values in color-name-rgb-alist were
> incorrectly scaled from 8-bit variants, and need to be amended.
Actually, it does not make sense to scale in that way. #3a7 really
should be the same as #3333aaaa7777, so that #fff is the same as
#ffffffffffff, pure white.
Somebody should tell the X people to do that. I just have no idea who
to tell, and it would appear that there is a bit of previous art that
might rely on the current behavior...
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum
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