[cairo] cairo-pdf color profiles?

[Adam Goode]

MenTaLguY wrote:
> We've been trying to beat the cairo-based PDF export into shape for the
> next Inkscape release, and one of the most obvious issues that comes up
> is that the colors in PDFs exported via cairo take on strange "muddy"
> casts when viewed in acroread.  Should we be using a different color
> space?
> 
> -mental
> 
>

The blending color space needs to be set for each page transparency
group. Otherwise, The RGB color values will be converted to CMYK in a
system-dependent way, blended in that space, and converted back to RGB
for display (in a system-dependent way). The result of all this means
that PDFs with any transparency will look totally different between
different versions of acroread and between the same version of acroread
on different platforms.

See 7.2.3 and 7.3.6 in the PDF reference version 1.6.

Ultimately, a PDF should have something like this:

<</Group <</CS /DeviceRGB
/S /Transparency
>>

in the object defining your page.



Adam


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