Re: [css4-color] HLC <= CIE-La*b*

On Monday, November 21, 2011, 6:53:09 PM, Tab wrote:

TAJ> On Mon, Nov 21, 2011 at 6:06 AM, Kevin Bortis <> wrote:
>> On Tue, Nov 15, 2011 at 3:56 PM, Christoph Päper
>> <> wrote:
>>>  hlc(<angle>, <percentage>, <percentage>)

>>>  hlc(240deg, 80%, 15%)
>>>  hlc(0.667turn, 0.8, 0.15)
>>>  hlc(267grad, 204, 38) …

>> Degrees are the only practical solution here. I don't know anyone who
>> is using turns for color angles. The only other solution would be rad,
>> but this is not practical because PI is a never ending floating point
>> number.

TAJ> In practice, people use degrees, sure.  That doesn't mean that it's a
TAJ> good idea to force people to use degrees, 

In practice, people use only degrees, as an untyped unitless number. That doesn't mean that its a good idea to force people to use angular unit identifiers, just so that they could in theory also use radians or turns (which no-one has asked for or presented a use case for).

TAJ> Again, hiding the unit behind a unitless number is an anti-pattern.

Diverging from current industry practice is also an anti-pattern.

TAJ> I haven't yet learned enough of hlc to know if either of these apply,

I'm familiar with it (and it is usually LCH, by the way, not hlc) and neither of them apply. No-one uses radians for the hue; the lightness is not a percentage.

TAJ> I agree with the desire for a new color palette that's not based on
TAJ> the idiotic X11 scheme.  This idea has history stretching back a
TAJ> decade, to when the 'color' property was first being debated in CSS.

Yes. (I recall proposing such a system, around 1994 or 95).

TAJ> I support reopening those discussions and coming up with a sane color
TAJ> palette designed around base colors and optional keywords like "light"
TAJ> or "very dark", etc.  I'm neutral as to whether we define this in
TAJ> terms of hlc or some other color scheme, because I don't know enough
TAJ> about the merits, but having perceptually even palette would be nice.

It would make sense to define it in Lab, because the merit of using named colours is that you use a name not a value, so there is no particular benefit to using LCH instead of Lab.

 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups

Received on Tuesday, 22 November 2011 14:40:59 UTC