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qtpdfprintingpostscriptcups

QPrinter::PdfFormat to printer using generic postscript driver

My printer is setup using a generic postscript driver in a Linux environment with CUPS. I have an application using Qt 4.8.7 QPrinter for doing printing. If setting the output format to QPrinter::PdfFormat, what is actually happening?

  1. QPrinter realizes that the target printer is a postscript printer and output postscript anyway.
  2. CUPS is converting the document from pdf to postscript before sending it to the printer.
  3. The document is sent to the printer as a pdf and it happens to support it. Doing the same thing using another that does not support pdf would not work.
  4. Other (then please explain what :)

Update: I use CUPS v.1.6.3

Solution

  • To some extent this is going to depend on what version of CUPS you have installed. I believe recent versions of CUPS use PDF as their internal format, so when you print a file, it is converted to, or preserved as, PDF and then passed along the CUPS pipeline in that fashion.

    Processing takes place on the PDF file, I don't know if that ever involves conversion to other formats, but I guess it might (eg N-Up conversion for example).

    Finally, the PDF reaches the point of actual printing, at which point it needs to be converted (or rendered) into something the printer can understand. CUPS needs to know the page description language the device supports, I can't tell you how it knows that, presumably there is some configuration somewhere.

    If it knows that your printer supports PDF then I believe the PDF will be delivered to the printer. If it understands PostScript then it will be converted to PostScript and that will be delivered to the printer. Other formats will require other printer drivers.

    So in short it kind of depends on the version of CUPS you have installed, and how the pipeline is configured. I seem to recall that you can get this information out of CUPS, though I can't remember how to do so I'm afraid.

    Hopefully someone with better CUPS experience can tell you more, or how to discover the filter setup you have. Browsing the man pages they do seem to be a little out of date with the way I thought CUPS currently worked.