[poppler] Implementing overprint in Splash

[Albert Astals Cid]

A Dijous, 24 de març de 2011, Thomas Freitag va escriure:
> I don't know if this patch is useful without the outstanding overprint
> patch for Splash, but I finished implementation of the two new options:
> 
> -overprint renders the PDF in in splashCMYK8 first and converts the CMYK
> Splash bitmap to RGB during writing (compiler switch SPLASH_CMYK must be
> set on pdftoppm and on poppler library). It's implemented for png, jpeg
> and tiff, tested for png and jpeg but should work with tiff, too.
> USE_CMS is not implemented in the moment, the conversion from CMYK to
> RGB is done with a copy from the GfxState-routines.

Why copy the functions?

> -jpegcmyk produces a jpg in CMYK colorspace (compiler switch SPLASH_CMYK
> must be set on pdftoppm and on poppler library).
> 
> Because overprint is not implemented yet, the overprint option changes
> nothing in the moment. So this option can be used as a zero state for
> overprinting to see which PDF renders differently with the outstanding
> first implementation of overprinting.

Don't understand this.

Albert

> 
> Thomas
> 
> Am 21.03.2011 20:47, schrieb Albert Astals Cid:
> > A Dilluns, 21 de març de 2011, Thomas Freitag va escriure:
> >> Hi all!
> >> 4. Support of overprint in pdftoppm
> >> To support overprint in pdftoppm we have to enable SPLASH_CMYK in
> >> pdftoppm and use it for rendering. But all output formats defined in
> >> pdftoppm uses RGB as output colorspace, and even the main output formats
> >> ppm and png do not support CMYK colorspace. Therefore we have to
> >> possibilities to support overprinting in pdftoppm:
> >> a) The easiest way would be to specify a new output format like i.e.
> >> jpegcmyk and create a jpeg image in CMYK colorspace where overprinting
> >> will be supported.
> >> b) The more interesting way is to add a new parameter -overprint, when
> >> set use splashCMYK8 as colorMode and when writing the output file
> >> convert it to RGB. The first implementation could use the poor
> >> colorspace conversion in Splash to convert the CMYK bitmap to RGB, but
> >> we should think of use little cms to do that work for us, which of
> >> course means that compiling pdftoppm will become more complex.
> >> 
> >> Any suggestions from the community to point 4?
> > 
> > Both seem interesting :-)
> > 
> > Albert
> > 
> >> Thomas
> >> 
> >> _______________________________________________
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> >> poppler at lists.freedesktop.org
> >> http://lists.freedesktop.org/mailman/listinfo/poppler
> > 
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> > .