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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 13:12:19 -0700
Message-ID: <CAAWBYDDyrt95vJPwfHZhsX5=7UZooX32KYFftwrqv42uY8md1g@mail.gmail.com>
To: Dirk Schulze <dschulze@adobe.com>
Cc: Simon Sapin <simon.sapin@exyr.org>, www-style list <www-style@w3.org>
On Thu, Sep 12, 2013 at 11:38 AM, Dirk Schulze <dschulze@adobe.com> wrote:
> On Sep 12, 2013, at 5:41 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:
>> 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.)

That's the sRGB gamut, yes.  But the rgb() function intentionally
allows you to specify values outside of that gamut, with the values
clamped to the device's gamut at an undefined point in time when the
hardware gamut is known, with an undefined clamping strategy.

For example, there are some TVs with a fourth yellow pixel, which can
represent bright/pale yellows outside the sRGB gamut.

All specifications should accept the possibility that colors will be
outside the sRGB gamut, and treat them appropriately.  Generally,
nothing special needs to be done at all.

~TJ
Received on Thursday, 12 September 2013 20:13:05 UTC

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