[poppler] Implement overprint in qt interface?

Tue Oct 16 13:49:15 PDT 2012

El Dilluns, 15 d'octubre de 2012, a les 07:25:54, Adam Reichold va escriure:
> Hello,
> 
> On 15.10.2012 07:15, Thomas Freitag wrote:
> > On 14.10.2012 22:58, Albert Astals Cid wrote:
> >> El Diumenge, 14 d'octubre de 2012, a les 19:41:26, Thomas Freitag va
> >> 
> >> escriure:
> >>> On 14.10.2012 17:21, Albert Astals Cid wrote:
> >>>> El Diumenge, 14 d'octubre de 2012, a les 13:47:29, Thomas Freitag va
> >> 
> >> escriure:
> >>>>> Hi folks!
> >>>>> 
> >>>>> Is there anybody in the community who wants the possibility to
> >>>>> simulate
> >>>>> overprint in qt library?
> >>>>> With the implementation of DeviceN support in splash this is quite
> >>>>> easy
> >>>>> now, so I can upload a patch.
> >>>> 
> >>>> Sure, why not? Let's see the patch :-)
> >>> 
> >>> Okay, here it is.
> >> 
> >> The two new methods are missing @since markers (and also i think the
> >> documentation of the two methods could be a bit more explanatory)
> > 
> > @since: I thought that You insert it when You commit it. If I would
> > insert 0.22.0 You have to change it if You will not have the time to
> > commit it :-) or I need to change it and have to upload a new patch if
> > You will not have the time :-(
> > Explanatory: Okay, but this will be hard. For those who know what
> > overprint is the documentation is self-explanatory, for others I need to
> > write reams. What's about to insert the link to
> > http://en.wikipedia.org/wiki/Overprinting?
> > 
> >> Also why are you calling it "overprint preview"? How is it a preview?
> > 
> > To be honest, I haven't really thought about that. Probably I choose
> > that name because it is also introduced in GlobalParams with that name.
> > But also in the acrobat reader preferences it is called "Use overprint
> > preview". And because not all RIPs support it (i.e. RGB printers) it is
> > indeed something like a preview (for RIPs which support it).
> 
> I'd say that insofar as this simulates the subtractive colour mixing
> that layer of colour in actual print will display which is as you said
> not really possible using the additive colour mixing of computer
> monitors, the displayed output is a mathematical simulation or a preview
> of the real physical effect in printing.
> 
> >> Given that overprint only works if defined(SPLASH_CMYK) you should
> >> make the
> >> setter return a boolean that says if the set worked or not (i.e. make
> >> it fail
> >> if !defined(SPLASH_CMYK))
> > 
> > Gotcha. I thought about that and disable / enable the option in okular
> > if the format generator doesn't support it. But because I'm not familiar
> > enough with okular I defered it and then forgot it...
> > I'll insert it in QT when I get answers to the other points.
> 
> Another option would be to expose this via the RenderHints flags? But of
> course, this couldn't return a bool as this would have to change the
> signature of Poppler::Document::setRenderHint.
> 
> But considering how this will be used: Wouldn't it be better to have
> something like "static bool supportsOverprintPreview()" because I want
> to check whether this is enabled before I try to set it. (E.g. not even
> showing the user this option as Thomas suggested.) (This could also be
> combined with the IMHO cleaner RenderHints approach.) (And since the
> value of SPLASH_CMYK is known at build-time, maybe this could just as
> well be exposed as a preprocessor definition, like
> POPPLER_QT4_OVERPRINT_PREVIEW?)

Preprocessors are evil, a the function and the render hint make sense to me, 
what do you think Thomas?

Cheers,
  Albert

> 
> Best regards, Adam.
> 
> P.S.: Btw., I think it would make sense to call the threadsafe define
> "POPPELR_QT4_THREADSAFE" instead of "POPPLER_QT_THREADSAFE" as well
> since there might be another Qt frontend sometime in the future with
> different threading properties.
> 
> > Cheers,
> > Thomas
> > 
> >> Cheers,
> >> 
> >>    Albert
> >>> 
> >>> In a few places it has already a similar
> >>> implementation than in bug 50992 (thread safe), because changing the
> >>> overprint option also meant that we need a different SplashOutputDev
> >>> instance. But You probably also want to test it in okular? Even if we
> >>> are here not on an okular list, I attach the okular patch here, too.
> >>> Also here, it has already the changes from bug 50992. But because
> >>> POPPLER_QT_THREADSAFE is not defined here, it doesn't make any
> >>> difference, so I let these changes as they are. BTW, I'm not really
> >>> familiar with qt programming, so most changes in okular are more or less
> >>> a (hopefully) best guess.
> >>> 
> >>> Cheers,
> >>> Thomas
> >>> 
> >>>> Cheers,
> >>>> 
> >>>>     Albert
> >>>>> 
> >>>>> For everybody who doesn't know anything about overprint I attach three
> >>>>> screenshots which shows the implementation in okular.
> >>>>> (This is not fake, I made a small apprentice piece today morning :-) )
> >>>>> 
> >>>>> Cheers,
> >>>>> Thomas
> >>>> 
> >>>> _______________________________________________
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> >>>> poppler at lists.freedesktop.org
> >>>> http://lists.freedesktop.org/mailman/listinfo/poppler
> >>>> 
> >>>> .
> >> 
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> >> .
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