[CREATE] ORA spec: adding additional layer effects

[Chris Lilley]

On Saturday, February 25, 2012, 10:13:31 PM, Alexandre wrote:

AP> On Sun, Feb 26, 2012 at 1:10 AM, Alexandre Prokoudine
AP> <alexandre.prokoudine at gmail.com> wrote:
>> On Sun, Feb 26, 2012 at 1:03 AM, Andrew Chadwick wrote:

>>> Is there any reason why GIMP and Krita aren't (by quick
>>> experimentation and/or code analysis) using this?

>> It was a too quick one :)

>> GIMP relies on Lab for doing compositing in Color blending mode when
>> "Use GEGL" checkbox is enabled.

AP> Ah, no :)

AP> commit 18603ac192493296b191197a3e2b62c710398afd
AP> Author: Martin Nordholts
AP> Date:   Sun Aug 2 21:35:10 2009 +0200

AP>     Bug 401754 – Port Hue, Saturation, Value to CIE LCH

AP>     When using GEGL for the projection, use CIE LCH for the Hue,
AP>     Saturation and Value layer modes, just as we already do for the Color
AP>     layer mode. The Value layer mode will later be renamed to Lightness
AP>     since that is the semantics it has now.

Assuming that means LCHab (as opposed to LCHuv) then SVG2 will have that one, as well.

The advantage over HSV or HSL is much better perceptual uniformity. The disadvantage is that interpolation can produce out of gamut colours, which need to be clipped or, better, gamut mapped.

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