[Kde-print-devel] [Bug 150155] kprinter "Print to file" gives broken PDF or Postscript that won't convert to PDF.

Thu May 1 14:16:10 CEST 2008

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http://bugs.kde.org/show_bug.cgi?id=150155         

------- Additional Comments From pfeifle kde org  2008-05-01 14:16 -------

Short advice:
-------------

When using kprinter's "Print to PDF file" feature with TrueType fonts, disable the "font embedding" of Qt first. Then the resulting PDF will contain the real TrueType font. Otherwise it will contain a pixelized, crappy looking, non-standard named "Type 3" font that Qt created because it cannot embed real TrueType fonts into its "I-can-only-do-PostScript-Level-1!" printfile.

Long explanation:
-----------------

The problem with printing from Qt-based applications over the last 10 years are
these:

  1) Qt, when generating PostScript for printing, can only support PostScript
Level 1.

  2) Qt can't handle TrueType fonts well when it comes to printing.

Taken together, these two points mean: Qt cannot embed the real, original TrueType fonts into its PostScript Level 1 printfile output; instead, Qt converts TT fonts to a sub-setted (and even crappy-looking at that!) "Type 3" PostScript font, and embeds this replacement font instead.

To add insult to injury, the font names used for its embedded "converted to Type 3 fonts" by Qt do not comply with the font naming standards for subsetted fonts that were laid down by Adobe in the official PostScript specifications. Try to run this command:

     pdffonts a-pdf-file-made-by-kprinter.pdf

and you will obtain something like that:

name                                 type         emb sub uni object ID
------------------------------------ ------------ --- --- --- ---------
[none]                               Type 3       yes yes no       9  0 
[none]                               Type 3       yes yes no      11  0 
[none]                               Type 3       yes yes no      19  0 
[none]                               Type 3       yes yes no      33  0 
[none]                               Type 3       yes yes no      39  0 
Symbol                               Type 1C      yes no  yes     44  0

when you really should be seeing this:

name                                 type         emb sub uni object ID
------------------------------------ ------------ --- --- --- ---------
OMMOFH+Optima                        TrueType     yes yes no     247  0
OMMOAN+Arial,Bold                    TrueType     yes yes no     250  0
OMMOBJ+Arial                         TrueType     yes yes no     253  0
OMMPFE+TimesNewRoman                 TrueType     yes yes no     266  0
OMMPHE+Arial,Italic                  TrueType     yes yes no     269  0
Symbol                               Type 1C      yes no  yes    318  0

This TT font handling "feature" of Qt has many more drawbacks:

1.  PDFs created from PostScript that was output by a typical Qt application don't only look ugly....

2.  ....and therefor do get downrated when it comes to "usability"...

3.  ....but they also are not "searchable"....

4.  ....and they don't let you extract the contained text ("pdftotext"),....

5.  ....they don't work with a screenreader....

6.  ....and hence are a complete failure when it comes to "accessability".

You can have a look at these two PDF files I did <a href="http://bugs.kde.org/show_bug.cgi?id=140546">generate quite some time ago</a> which show all 6 points from above in a comparison. The same OpenDocumentText (.odt) file was used as the base file:

-- to "Export to PDF" from OpenOffice.org: http://bugs.kde.org/attachment.cgi?id=19402&action=view
-- to "Print to PDF file" from KWord: http://bugs.kde.org/attachment.cgi?id=19403&action=view

These problems haven't been fixed (or even touched) by Trolltech for over a decade of Qt1-Qt3(-Qt4) development. At the same time, there have been quite a few bugs about it in Trolltech's internal (and published) bug tracking system. And various Trolltech promises ("will be fixed in next version") made inside their bug tracker have never
happened....

So, Qt sux donkeyballs when it comes to PostScript and TT font handling in PS print files. 

To be sure: the company's reason for that neglect is not evil-mindedness on the part of Trolltech. It seems there was just not much money to be made from "make printing work really well", while at the same time the effort to make that happen is considerable, and people with the appropriate Knowhow are very rare. 

Coding any stuff related to "printing" also isn't as "sexy" as coding for desktop bling-bling (see all these Compiz, Beryl and Plasma efforts) or audio players... so you'll not stand a big chance to have this tackled from the side of the "I'm-just-coding-for-my-personal-fun-or-to-scratch-my-own-itches" FOSS crowd 

"Oh, wait", I hear you saying, "there is Scribus, which is a Qt application, and it produces excellent PostScript or PDF output, and has no such problem with TT fonts."

That's true. But it is only true because the Scribus developers didn't rely on Qt when it came to generate their print files. They did their own thing on that field. They had to. Otherwise, they'd have to suffer from the same problem that
KDEPrint (up to KDE 3.5.9) did and still does....

"So isn't there a workaround when you want to generate PDFs via KDEPrint's 'Print to PDF' feature?", you ask.

Yes, there is:

----------------------------------------------------------------------------------------
  ==> Disable "Font embedding" when KDEPrint-ing documents that contain TrueType fonts.
----------------------------------------------------------------------------------------

You can avoid Qt's font embedding by 

 * running "kaddprinterwizard --kdeconfig", 
 * select "TT fonts", 
 * disable "Embed fonts with PostScript data when printing".

The net effect of that is that the original TrueType font used by the document will be referenced only by name in the resulting PostScript file. If the next step in print processing then is running Ghostscript on that PostScript file (in the case of kprinter's "Print to PDF" that *IS* the case), Ghostscript will try to use the real TT font and embed that into the file (and that way avoid an already embedded, crappy looking, badly usable, non-accessible, not-able-to-read-aloud-by-KSST, un-searchable Type 3 font as is generated by Qt).

What about the future? 

Qt4 introduces "export to PDF" and therefor seems to be much better for print fidelity and quality. However, the Qt-app needs to take advantage of that...

Whenever there is a Qt/KDE app that still outputs PostScript, you're still treated with Level 1 PostScript and with the dreaded "I-converted-your-nice-TrueType-fonts-into-my-crappy-quality,-ugly-looking,-pixelized-Type-3-fonts" feature.