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Re: Named colors in SVG

From: Jeremias Maerki <dev@jeremias-maerki.ch>
Date: Wed, 16 Jun 2010 10:06:24 +0200
To: www-svg@w3.org
Message-Id: <20100616100101.860A.60BA733C@jeremias-maerki.ch>
Chris,
for comparison, it can make sense to check what some commercial XSL-FO
implementations did to support additional color spaces. The two I've
check both support an optional tint value:

http://www.antennahouse.com/xslfo/axf5-extension.htm#rgb-icc
http://www.renderx.com/reference.html#Color_Specifiers

On 16.06.2010 09:53:14 Jeremias Maerki wrote:
<snip/>
> > JM> --- tint support
> > 
> > JM> The PDF and PostScript specifications allow for a "tint" value for
> > JM> Separation colors. I was wondering if it made sense to add an optional
> > JM> tint value to the icc-named-color function. The spec would then be:
> > 
> > JM> <fallback> icc-named-color(<name>, <namedColor>[, tint])
> > 
> > JM> Valid values for the parameter "tint" are in the range 0.0 to 1.0. The
> > JM> value 0.0 represents the minimum amount of colorant that can be applied;
> > JM> 1.0 represents the maximum. In the absence of the tint parameter, the
> > JM> initial value is 1.0.
> > 
> > JM> Example:
> > JM> <circle fill="#8080FF" icc-named-color(MyColors, SpecialBlue, 0.5)"/>
> > 
> > That is an interesting suggestion. However, would the result be an
> > actual, colorimetrically defined color? Or would it be a recipie, which
> > only results in a visible color on the output device?
> > 
> > In other words if SpecialBlue has LAAB coordinates Lb ab wb and the
> > current white has LAB coordinates Lw aw bw, is there an equation that
> > gives the LAB coordinates of thre 50% tint? Or does that require press
> > characterisation?
> 
> You lost me a bit on the terms (I'm still learning). But essentially,
> that's the problem I've also stumbled across: how to calculate the Lab
> or XYZ coordinates for values between the spot color and the white point?
> I really don't know just yet. I've simply seen that PDF offers that tint
> value when using a Separation color space. I don't need it myself, but I
> found no equivalent (other than the alpha/transparency/opacity value) in
> the color functions of the SVG Color WD. Maybe the tint is simply used
> for half-toning. But on modern digital printers the matter is different
> since the colors are still mixed for spot colors.
> 
> > This for example does result in a color:
> > 
> > <circle fill="#8080FF" icc-named-color(MyColors, SpecialBlue)" 
> >   fill-opacity="0.5"/>
> 
> I have no idea if it's the same as tint. Transparency is usually handled
> in PDF in a different place (i.e. in addition to the tint). Anyway, this
> is really out of my league right now and I'm trying to catch up.
<snip/> 




Jeremias Maerki
Received on Wednesday, 16 June 2010 08:06:48 GMT

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