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Re: [css4-color] #RGBA

From: Alan Gresley <alan@css-class.com>
Date: Mon, 13 Sep 2010 04:14:47 +1000
Message-ID: <4C8D1897.3050809@css-class.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Lea Verou <leaverou@gmail.com>, www-style@w3.org
Tab Atkins Jr. wrote:
> On Sat, Sep 11, 2010 at 8:31 AM, Lea Verou <leaverou@gmail.com> wrote:
>> HSL (and HSV) are just different (more intuitive) ways to refer to the RGB
>> color space. They have the exact same gamut.
>>
>> From http://en.wikipedia.org/wiki/HSL_and_HSV:
>>
>> HSL and HSV are the two most common cylindrical-coordinate representations
>> of points in an RGB color model, which rearrange the geometry of RGB in an
>> attempt to be more perceptually relevant than the cartesian representation.
> 
> Right, I'm not disputing that.  I'm saying precisely what that
> wikipedia quote is - hsl is a different geometry applied to the space.
> 
> ~TJ


I guess you are wondering what space that is. It is not what is seen 
on the swatches in CSS3 Color [1] which shows expansive distortion 
heading towards the right or the swatches on the page on Wikipedia [2] 
which shows expansive distortion heading towards the top. It has 
uniform changes (or steps) through sRGB color-space.


<http://css-class.com/test/css/colors/hsl-in-sRGB-color-space.htm>


Imagine that you are looking at a floating cube from below.


To see decreasing saturation but with the same hue and lightness, 
enter #ffff00 (yellow) into a color picker and allowing for rounding 
errors, decrease the saturation to 128 and you will have #bfc040 
(#bfbf3f). Decrease the saturation again to 0 and you will have 
#808080 (#7f7f7f). This traces the colors from yellow to mid gray.

To see changes is lightness but with the same hue and saturation, 
enter #ffff00 into a color picker and slide the lightness up and down 
and allowing for rounding errors you will trace the colors from the 
vectors of yellow to white and yellow to black.


The same applies for blue and the aqua and red field below.


1. <http://www.w3.org/TR/css3-color/#hsl-examples>
2. <http://en.wikipedia.org/wiki/HSL_color_space#HSL>



-- 
Alan http://css-class.com/

Armies Cannot Stop An Idea Whose Time Has Come. - Victor Hugo
Received on Sunday, 12 September 2010 18:15:24 GMT

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