[Qt3] FYI: Print speed issue PostScript / Unix

[Till Oliver Knoll]

For those who still use Qt 3.x (like us ;), there's another good reason 
to upgrade to 4.1:

In the thread 
http://lists.trolltech.com/qt-interest/2005-09/thread01145-0.html Joseph 
 noticed that printing on Unix is very slow compared to other applications.

We've had the same trouble, printing for a 2000 x 2000 pixel image took 
around 2.5 minutes (only Unix, on Windows printing is as expected around 
30 seconds). Compared to Gimp (roughly same resolution):

  Qt 3.3.5: ~2.5 minutes (!)
  Gimp:     ~30 seconds

I've had a look at the generated PostScript: it seems that Gimp produces 
uncompressed PostScript image data whereas in Qt 3.3.5 the data is 
compressed:

  Qt 3.3.5: ~780 KByte PostScript (which is actually good)
  Gimp:     ~9.8 MByte PostScript

Now our (somewhat older) HP Laserjet 4100N seems to take some time 
decompressing this data (also KGhostView is way slower displaying the Qt 
generated PostScript compared to the Gimp generated PostScript).

The code in question is in QTDIR/src/kernel/qpsprinter.cpp, the compress 
function is called on the image data. I've tried to quickly hack it, but 
didn't succeed so far and I don't want to spend too much time on it.


So the GOOD news: In Qt 4.1 I've quickly done another print test:

  Qt 4.1: around 17 seconds :)
  size:   ~1.9 MByte

Indeed the compression scheme seems to have changed in the generated 
PostScript.


Cheers, Oliver


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