Both SVG and XSL-FO are using sRGB color space by default. The color
industry came up with the ICC standard for non-sRGB colors which is what
the SVG and XSL working groups chose for non-RGB colors. Unfortunately,
many people don't seem to understand how this works and many creation
tools don't support it. That's why people keep falling back to
(uncalibrated) CMYK. FOP's basic support for CMYK is basically a
concession to that. It's a proprietary extension, too. AFAIK, Batik
hasn't been confronted with this too much until now. It doesn't support
uncalibrated CMYK at the moment, so at the moment you can't use the same
approach in both XSL-FO and SVG.

Best practice as recommended by the editors of the SVG and FO standards
is:
- Use ICC color profiles
- in FO, use rgb-icc(num, num, num, <name>, num*)
http://www.w3.org/TR/xsl11/#expr-color-functions
- in SVG, use <color> icc-color(<name>, num*)
http://www.w3.org/TR/SVG11/painting.html#SpecifyingPaint

But yeah, you probably don't have tool support for that. And you can't
use EPS in PDF. Leaves you rasterizing SVG to CMYK bitmaps at the moment. :-(

Of course, proprietary support for uncalibrated CMYK colors could be
added to Batik and FOP's PDF transcoder in the same way it was added to
XSL-FO support. But IMO it's the wrong way.

Essentially, we need four things to make this work as it is supposed to:
1. SVG and XSL working groups should sit together and harmonize their
color efforts. I've mentioned that to them before so they are aware.
2. People (software developers, content creators, print shop employees
etc.) should learn about ICC colors.
3. SVG creation tools need to start supporting ICC colors.
4. FOP and Batik need to be reviewed if they handle the ICC colors
correctly in every case. The functionality should be there but due to
the lack of actual real-life projects this is probably not well tested.

I'm available to help with improving color support in Batik and FOP. I
think it's an important aspect of the two applications but there's still
some way to go.

On 11.09.2008 11:30:25 Maximilian Gaerber wrote:
> Hi all,
> 
> I read some posts about cmyk integration in FOP and so far it seems to 
> work for my purposes when using it directly in XSL-FO. The bigger issue 
> is with SVG:
> 
> - Illustrator or Inkscape will only export SVG with RGB color codes (HEX).
> - I could post-process the SVG graphics through xsl and add the cmyk 
> information
> - But right now it seems the PDF output of FOP is not able to handle 
> these colors
> 
> What would be "best practices" at the moment with SVG, FOP and cmyk 
> colors? Don't use? What else? Go back to EPS or rasterize the SVGs?
> 
> Regards,
> 
> Maximilian Gärber
<snip/>


Jeremias Maerki


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