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

From: Rik Cabanier <cabanier@gmail.com>
Date: Tue, 2 Aug 2011 09:13:56 -0700
Message-ID: <CAGN7qDDKECpNnBoh+FoQU3+cCbfyDcuD6p4eQF7Szn777hRQpw@mail.gmail.com>
To: Nick Hofstede <Nick.Hofstede@inventivegroup.com>
Cc: "www-svg@w3.org" <www-svg@w3.org>
Hi Nick,

how would you match the black in the background with the black in the image?
You might not know what profile was used to create the image.
I think the website is warning you not to rely on Photoshop's black when you
do CMYK. This is really a design error.
If you can't fix the image, you could use the eyedropper to get the numbers
and match the border with the rich black. Hopefully nothing else will touch
that box :-)

Can you tell me what you mean by:
> That way any gradient in the image (the example image doesnít really have
one, but imagine a picture that fades to black on the edges) is nice and
continuous.
How would rich black help with that?

> Lcms2 added this extra option (no-preservation, black only, black-plane)
by duplicating its intents
Reading the comments, I don't really understand how this feature works. Is
this done just through ICC?
InDesign introduced a way of doing this a couple of releases ago. They call
this feature "preserve numbers". see
http://indesignsecrets.com/getting-accurate-colors-when-printing-proofs-from-indesign.php
.
That page also has a short description how InDesign handles CMYK values.

Rik Cabanier
Adobe Systems, Inc


On Tue, Aug 2, 2011 at 12:14 AM, Nick Hofstede <
Nick.Hofstede@inventivegroup.com> wrote:

>  No, the profile on the image is correct. I want the image to use rich
> black. That way any gradient in the image (the example image doesnít really
> have one, but imagine a picture that fades to black on the edges) is nice
> and continuous.
>
> Therefore, if I put the image on a black background or want to put a black
> border on it, I want that black to be rich black as well.
>
> If weíre going to decide automatically that all solid filled black (and
> presumably gray) shapes and strokes will use preserve-black, this isnít
> going to happen.
>
> Thatís why I think we need an extra switch for the preserve black option.
>
> Lcms2 added this extra option (no-preservation, black only, black-plane) by
> duplicating its intents, but an optional switch seems cleaner to me. (
> http://sourceforge.net/apps/trac/mpc-hc/browser/trunk/src/thirdparty/lcms2/src/cmscnvrt.c?rev=3024see DefaultIntents[])
>
>
>
> Nick Hofstede
>
> R&D Manager
>
> *From:* Rik Cabanier [mailto:cabanier@gmail.com]
> *Sent:* maandag 1 augustus 2011 19:26
> *To:* Nick Hofstede
> *Cc:* www-svg@w3.org
> *Subject:* Re: minutes, SVG WG Seattle F2F 2011 day 3 - SVG Color
>
>
>
> Hi Nick,
>
>
>
> I think this is a case where you want to ignore the profile that is
> attached to the image and swap it out with the destination profile instead.
>
>
>
> There was a discussion at the f2f why we would need to swap out the
> attached profile. This seems to be a valid use-case for such a feature.
>
>
>
> Rik Cabanier
>
>
>
> On Mon, Aug 1, 2011 at 12:07 AM, Nick Hofstede <
> Nick.Hofstede@inventivegroup.com> wrote:
>
> 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 Tuesday, 2 August 2011 16:14:24 GMT

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