- From: MSP-Greg via GitHub <sysbot+gh@w3.org>
- Date: Tue, 20 Sep 2016 20:43:50 +0000
- To: public-css-archive@w3.org
MSP-Greg has just created a new issue for https://github.com/w3c/csswg-drafts: == [css-color] hsl values - integer or number? == I believe the current wd does a good job of explaining hsl vs rgb. See [6. HSL Colors: hsl() and hsla() functions](https://www.w3.org/TR/css-color-4/#the-hsl-notation), and the following section (6.1) on conversion. What it does not address is how an algorithm for hsl to rgb conversion should handle numbers, as opposed to 'integer' values. I believe the spec refers to hsl using 'numbers', and numbers are not restricted to being integers, see [CSS Values and Units Module Level 3 - 4.2 Real Numbers: the <number> type](https://www.w3.org/TR/css3-values/#numbers). I checked four browsers for conversion from hsl to rgb (using s = 100%, l = 50%). In this restricted 'color space', rgb (1,530) has 4.25 times the resolution of hsl (360) when hsl is computed using integer values. So I checked the browsers using a hue (h) value that varied from 0 to 6.9 by tenths. I found three different algorithms being used, three displayed only a green value that was a 'rounded multiple' of 4.25 (0, 4, 8, 12, 17, 21, 25). Of the three, two truncated, one rounded. Only one browser had all green integer values. See https://msp-greg.github.io/ct-hue-sat.html for the test I used. I did check that the painted rgb color matched the reported color. Given that monitor technology has changed quite a bit since hsl was introduced in 2003 or so, I think it would be helpful for hsl to have the same color range as rgb. Hence, can the spec reflect that? Thanks for your work... Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/506 using your GitHub account
Received on Tuesday, 20 September 2016 20:43:58 UTC