[Scribus] Images in PDF output

David Purton dcpurton
Mon Jan 10 13:43:07 CET 2005

On Sun, Jan 09, 2005 at 08:39:02PM -0500, Kobus Wolvaardt wrote:
> >the photograph in that document.  I create a PDF document from that  
> >scribus document and take it to be printed.  The photograph, however, is  
> >seriously washed out.  It appears washed out in the pdf when viewed  
> >on-screen, also.
> I also experience this. Correct me if i'm wrong, but it has to do with the  
> conversion from rgb->cmyk. I think that converting a file to cmyk with  
> photoshop or gimp (I dont know how good gimp supports this) and including  
> it into scribus might improve the color.

I think you are right in thinking that the problem lies in the RGB->CMYK
conversion. Scribus does not use colour profiles to perform the
conversion from RGB to CMYK when it outputs images.

As for starting with CMYK images - looking at how Scribus handles images
- I think this will not help.  I'm only just starting to have a poke
through the code to see what can be done about this issue for my own

So far it looks like Scribus does something like this when outputing
images to a CMYK colour space PDF (assuming you work with tiffs):

The tiff is loaded using TIFFReadRGBAImage (a libtiff function) and the
resulting RGB data dumped into a QT QImage class. In other words, no
matter what the tiff actually contains, an RGB image is loaded. I assume
that libtiff does not do anything cunning in its conversion from CMYK to

When outputing to postscript or a PDF for print, this RGB data is then
converted back to CMYK. Unfortunately, you will probably not end up with
the same data as in your original tiff, because a maximum black pullout
is applied by Scribus in the RGB->CMYK conversion. i.e., any pixel in
your original image that has data in the C, M & Y channels will be

> A while ago there was a discussion about cmyk images being changed when  
> exported as cmyk in scribus, and there was talk of exporting all cmyk  
> files unchanged to pdf. Is this true? There are companies who has very  
> harsh demands when it comes to the color of their ads and it would help if  
> I can export cmyk images (pdf's, eps's, tiff's) without their color being  
> altered.

As far as I can gather it is currently impossible to do this in Scribus.
It will also be a *big* pain to change, because Scribus relies very
heavily on the QT QImage class to deal with image data. The QImage data
knows nothing about CMYK colour space. :(

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