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RE: minutes, SVG WG Seattle F2F 2011 day 3 - SVG Color

From: Nick Hofstede <Nick.Hofstede@inventivegroup.com>
Date: Mon, 1 Aug 2011 07:07:56 +0000
To: "www-svg@w3.org" <www-svg@w3.org>
Message-ID: <BC885F9E3DB48248A4C9FC7F2C57215C10883A2E@Hoefnix.dc.intranet>
Quick note on the black preservation:

    ChrisL: last issue is preserving black.
    ... For example, in ICC if you specify cmyk(0,0,0,1),
    color-management systems tend to have a switch that specially treats
    that value.
    ... So even if the system does color-manipulation normally, that one
    color will instead stay solid, total black.
    ... This is so black text stays pure black and doesn't mix in other
    colors.
    ... So, similarly, we need to see if we need it, and see if it's an
    input or output feature.

    cabanier: We have it in InDesign, and it's an output feature there.
    ... So we have some special cases there again; you don't want to
    preserve black on an image.

    ChrisL: So that's basically actually being an input feature.

    heycam: Does it make sense to have this controllable on images, or
    if we can magically just apply it to solid-color fills and strokes?
    ... Also, if you have some colored shapes which are composited
    together, and you happen to get black out of that, should that be
    preservable?

    TabAtkins_: So it sounds like we can just specify that solid-color
    strokes and fills automatically preserve black, and nothing else
    does. It can be applied on output, and doesn't need to be specified
    on input.

    cabanier: So we look at the operator on printing - if a shape is
    filled with an image or gradient, we don't preserve black. If it's
    filled with a color, we preserve.

    TabAtkins_: So if you composite a partially-transparent gradient
    over a black rectangle, you wouldn't preserve the black in it.

    heycam: So basically, for any image, track if the result color comes
    partially from a gradient or image. If so, don't preserve black;
    otherwise, preserve it.

    TabAtkins_: So it sounds like we can do this automatically at the
    end, and thus don't need a property for it.

    heycam: And in PDF, it's not controllable; it just happens
    automatically.

I'm not sure automatically deciding when to use black preservation is a good idea. I don't think you can always deduce it automatically and I think you should therefore be able to specify it.
Consider the use case talked about here for example:
http://www.blog.spoongraphics.co.uk/articles/the-ultimate-guide-to-designing-with-black

If you would create this in SVG your underlying rectangle would become black-preserved black, and the black from the image would be rich black.
You're going to want to be able to trigger rich black on the solid-color fill.

With kind regards,

Nick Hofstede

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Received on Monday, 1 August 2011 07:08:20 GMT

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