[Scribus] False colors in print and pdf output?!

[Oliver Schulz]

Hi all,

i got the following problem with Scribus (1.3.3.3):
When I print with "Apply ICC Profiles" enabled or
export PDF with "Use ICC Profile" disabled for images,
the color management seems to malfunction.

Background: I want to do color-corrected printouts
on an inkjet printer and generate PDF's which
are color-corrected for that printer (or a specific
press) and will print accordingly. Sadly, not all
printers really support PDF-X/3 ...

To find out a bit more about the problem, I used
a test document showing the same image encoded in
four different color spaces: sRGB (narrow gamut RGB)
and BestRGB (very wide gamut RGB), ISO-coated (CMYK)
and a custom Inkjet profile (CMYK). All images were
generated from the original sRGB one by relative
colorimetric transformation. All rendering intents
in Scribus were set to relative, too.

Inside Scribus (color management enabled, calibrated and
profiled display) the four images on the page look
exactly the same. With the print preview option enabled,
there are tiny differences. All as expected.

I tested several exports, each with two different
printer profiles (the same as in the CMYK images).

Here are the results (first the ones that seemed ok):

PDF-1.3 for Screen/Web: The four images look identical
in acroread, PDF contains all four images converted
to common RGB space (CalRGB?), PDF contains no color
profiles. Color managed transform seems to be done here
in Scribus. Output doesn't depend on printer profile set
in Scribus.

PDF-1.3 for Print with "Use ICC Profile" ENabled for
images or PDF-X/3: The four images look identical
in acroread (not in XPDF, seems not to support profiles)
PDF apparently contains the original image data and
profiles. Output doesn't depend on printer profile set
in Scribus.
When printed from Adobe Reader, the resulting PS
looks ok in Ghostview, ICC profiles seem to be
correctly converted to CSA and CRD profiles which
Ghostscript then uses for color-correction.

Printing (PS output), "Apply ICC Profiles" DISabled
(printing to file, display with gs): The four images
look different, but quite ok. Apparently, the RGB images
are converted to CMYK by a generic transform, no color
management is done at all (why?). Images look a bit different
because they're encoded in different color spaces. Output
doesn't depend on printer profile set in Scribus (why?).

So far, so good. Sorry for the long description of things
that did work. :-) I wanted to ensure that my color
management worked. 
Now for the things that didn't ...

PDF-1.3 for Print with "Use ICC Profile" DISabled for
images: The four images look completely different,
colors of the RGB-source images are _way_ off (e.g. yellow
goes green, ...). Results look quite different
for different printer profile settings, but horrible with
both. The CMYK-source images however look the same as in the
"Printing (PS output), "Apply ICC Profiles" DISabled"
case, independent of the printer profile.
PDF output contains all images in CMYK, no embedded profiles.
Obviously, Scribus does some color conversion with the
RGB-source images, and somehow uses the printer profile.
But the source-profiles don't seem to be used, cause
the results look different for the sRGB and the BestRGB
image. And why the horrible result?

Printing (PS output), "Apply ICC Profiles" ENabled:
Results are identical to PDF-1.3 for Print with
"Use ICC Profile" DISabled.
PS output contains all images in CMYK, no embedded profiles.

I really don't understand what's going on here - anybody
got an idea?
My setup: scribus-1.3.3.3, lcms-1.15, linux.


Another minor point: What should the "Apply ICC Profiles"
setting in the print dialog.really do? The tooltip says,
it embeds the ICC profiles in the print stream when color
management is enabled. But the resulting PS doesn't contain
any profiles, neither CIEbased nor ICCbased. Instead, Scribus
does color convertion (with the strange results described
above). However, when the option is disabled, everything
get's converted to CMYK without color management, even though
color management is enabled in Scribus. Is this intended?


I'd be glad for any help,

Oliver


P.S.: Thank you, Scribus team, for creating the software that
I had sorely missed for a long time!