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Re: [css-gcpm][css-color] device-cmyk() interaction with RGB-space colors.

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Thu, 12 Sep 2013 08:41:47 -0700
Message-ID: <CAAWBYDDaLGSJJqi9modoetQd2KYEHc471v8=xRf72Y7Yfp2K2w@mail.gmail.com>
To: Simon Sapin <simon.sapin@exyr.org>
Cc: www-style list <www-style@w3.org>
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.

~TJ
Received on Thursday, 12 September 2013 15:42:34 UTC

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