- From: Dirk Schulze <dschulze@adobe.com>
- Date: Thu, 12 Sep 2013 11:38:29 -0700
- To: "Tab Atkins Jr." <jackalmage@gmail.com>
- CC: Simon Sapin <simon.sapin@exyr.org>, www-style list <www-style@w3.org>
On Sep 12, 2013, at 5:41 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote: > On Thu, Sep 12, 2013 at 8:29 AM, Simon Sapin <simon.sapin@exyr.org> wrote: >> Hi, >> >> In CSS Color Level 3, all values of the <color> type (eventually) resolve to >> a (R, G, B, A) value. >> >> When multiple colors interact with each other in an interpolation >> (transition, animation, or gradient) or with alpha compositing >> (transparency), they do so in RGBA space. >> >> >> The addition of device-cmyk() changes that: not all colors are in the same >> space anymore. The spec needs to define how interpolation and alpha >> compositing works. >> >> Note that probably none of these cases are useful, we just need to pick >> something so that they’re well-defined. >> >> Possible suggestions: >> >> * Gradients whose color stops are not all in the same color space could be >> invalid. >> >> * I don’t expect any media to support both CMYK colors and >> transition/animations. But in case it happens, interpolating colors in >> different color spaces could switch at 50%, like interpolation of other >> discrete types. >> >> * Alpha compositing could be done in device CMYK space, after all RGB colors >> have been converted per a device-specific color profile. >> >> >> There may be further interactions with the Filter Effects and Compositing >> and Blending specs that need to be specified. > > If you ignore the gamut limitations, all color spaces are > interconvertible between each other, right? For example, a very > bright red might be rgba(120%, 0, 0, 1), but that's still a valid > number which can be interpolated with other rgba colors. For most specifications, colors are defined for a range of 0 to 255 (or 0.0 to 1.0). So 120% would go over this range which makes a difference for a bunch of specifications like Filter Effects, Blending, SVG. (No comment to the general intention to go beyond this range.) Greetings, Dirk > > ~TJ >
Received on Thursday, 12 September 2013 18:39:00 UTC