RE: [XaraXtreme-dev] Printing on Linux

[John Tytgat <john@xxxxxxxxxxxxxxxxx>]

In message <5056CBC646CB4047BB26120F4377DB719BA5F5@xxxxxxxxxxxxxxxxxxx>
          "Charles Moir" <CharlesM@xxxxxxxx> wrote:

> > John Tytgat said:
> > Apart from the smooth shadings, won't Xara's transparency 
> > features not cause various issues when printing via 
> > PostScript is done (unless you fallback on the giant bitmap 
> > printing approach) ?
> 
> As far as I'm aware there are no printer drivers, of any type that cope
> with transparency. Postscript doesn't, even Postscript 3 doesn't.

Exactly.  PostScript will never have transparency features added IMHO.

> It's only PDF 1.5 that introduced transparency.

Actually PDF 1.4 (introduced with Acrobat 5).

> But the printing industry
> standard, PDF-X, absolutely insists on no transparency at all simply
> because they know the unreliability and the scarcity of true support for
> transparency at the Postscript level.

True but that's because transparency technology and all its issues around
it were immature at the time the PDF/X standards (plurial !) were formed.
Actually at the first PDF/X standards (PDF/X-1 and PDF/X-1a) because
official, even DeviceN was outlawed because PostScript 3 features were
considered as not-yet-mature and there was not even talk on transparency
at all.

Note that there is a new PDF/X standard in the making which does allow
transparency/blendmodes to be used.  The pressure from the creative
applications became too much because of losing time and/or making silly
flattening errors when processing such files.

> So I believe you'll find all applications, Xara, Adobe, etc, flatten
> (i.e. rasterize) transparency where required.

Indeed, the current Adobe applications allow the user to control the
flattening (interactive or during output) and of course enforce it when
you go to an output format where transparency is not natively supported.

> Xara has used an
> intelligent flattening approach, rasterizing the minimum region
> necessary.  So if you create a flat color shape, and overlay a
> semi-transparent over part (or use any effect that requires transparency
> such as feathering, shadows etc) and we have no option but to output a
> combination of vector shapes with overlaid flattened bitmaps where
> required to simulate the correct output.

Sweet. :-) The technology and its challenges are not unknown to me.

> The bottom line is that users don't know or see this - printing drawings
> containing transparency just works, as it always has on Xara. i.e. the
> software does what is necessary in order to print the correct result,
> and if that involves printing parts of the image as bitmap, then that
> has to be.

I agree that should be the user story.  In reality I'm sure you will
agree this is a hard nut to crack if you don't want to compromise on
quality and absence of artifacts.

I don't know Xara well enough but if its transparency features are
reasonably mappable to PDF transparency model, then it would be a shame
to go over PostScript for printing on longer term. More and more RIPs
are handling transparency natively (instead of doing an internal PDF->PS
conversion and using their classic PS channel), especially with Adobe's
recent PDF Print Engine product.

Flattening still requires some choices to be made based on assumptions
of your final output resolution.  Wrong assumption either results in bad
quality, either in heavy output files and slow RIP timings.

John.
-- 
John Tytgat, in his comfy chair at home                                 BASS
John.Tytgat@xxxxxxxx                             ARM powered, RISC OS driven