Virtual Printer Driver for Windows

can you please help me with the following questions...

• If I need a virtual printer that will convert a PostScript stream to a different format, do I have to implement a virtual printer from scratch or implement a rendering plug-in?
• The rendering plug-in seems to support only certain customizations. Also the data invariably goes to the spooler which is not needed in this case.
• If I implement a virtual printer driver does it completely replace the Microsoft PostScript Driver or the Microsoft Universal Driver?
• Since my driver is virtual, does it matter if I write a P开发者_开发知识库ostScript compliant or a Universal Driver compliant one?
• Any other method to convert a printed document to a custom document format apart from implementing a virtual printer driver? Can I hook on as a port monitor or something? From what I could understand I guess not.

What you need is a port monitor. You can create a virtual printer using the Microsoft Postscript driver found in the WDK. You don't need to provide any code for this part, just an INF and PPD file to describe your virtual printer. Once you have that working and installed, users will then see your virtual printer when they print from an app. This printer will produce a stream of Postscript like any standard Postscript printer, which will then be sent to the printer's port monitor.

Now add a port monitor to handle converting the Postscript stream to whatever format you need. Port monitors are considerably easier to deal with than print drivers.

EDIT: Andy points out in the comments that v4 (ie, Win8) print drivers don't support custom port monitors. However, v3 drivers will still work in Win8.

I know this is old, but these answers would have helped me a couple months ago, when I started this project. I spent a lot of time creating a port monitor, only to find a much easier method in the end (see WritePrinter link below).

If I need a virtual printer that will convert a PostScript stream to a different format, do I have to implement a virtual printer from scratch or implement a rendering plug-in?

Rendering plug-in is what you want.

The rendering plug-in seems to support only certain customizations.

Correct -- you'll have to decide if it is enough for you.

Also the data invariably goes to the spooler which is not needed in this case.

This should not be an issue.

If I implement a virtual printer driver does it completely replace the Microsoft PostScript Driver or the Microsoft Universal Driver?

If you implement a rendering plug-in, it does not replace the PS/Uni drivers. The PS/Uni drivers are in fact used by a huge number (maybe 90%?) of all "printer drivers". OEMs that make printers don't want to write their own drivers, so they use the PS/Uni driver design -- some create UI plug-ins, some rendering plug-ins, some both, some neither.

Since my driver is virtual, does it matter if I write a PostScript compliant or a Universal Driver compliant one?

It depends what format you want the data in. If you want bitmap format, a Uni driver is better, if you want PostScript format, PS is better. If you want data for each line drawn, text out, and other GDI operations, then either is fine.

Any other method to convert a printed document to a custom document format apart from implementing a virtual printer driver? Can I hook on as a port monitor or something? From what I could understand I guess not.

Most people that want raw access to the PostScript data, usually to use GhostScript to convert to PDF or other format, use a port monitor to do this. For example, the Virtual PDF Printer that Adobe ships with the full version of Acrobat (Writer), uses a port monitor, and also a rendering plug-in and a UI plug-in, for the PSCRIPT5 driver.

The problem with a port monitor is that it doesn't run in the context of the user -- not in the context of the application/process doing the printing. It runs in the context of the print spooler, and requires a lot of hacks to figure out which user/session is doing the printing.

If you want bitmap data, to save as a JPG/BMP/PNG, for example, then just create a rendering plug-in for the universal printer driver and access/save the bitmap data inside IPrintOemUni::FilterGraphics.

If you want PostScript data, to use with GhostScript (or other library, or your own code) to convert to PDF or other formats, then just create a rendering plug-in for the PSCRIPT5 driver and access/save the PS data inside IPrintOemUni2::WritePrinter.

In either case, you want a rendering plug-in. If you want to easily display a UI while printing, and want your code to run in the same context as the user, and not the spooler service, then make sure you set your printer to print directly to printer -- bypass the spooler. If you use AddPrinter to install your printer, you would use the PRINTER_ATTRIBUTE_DIRECT flag.

Not sure I fully understand. You have an app that produces Postscript and you want to convert that to something else? If the application outputs the 'print ready' data then a new printer driver isn't going to help as the 'queue/driver' is just a way to get the data to the printer and not something that is creating the output file.

You might be best to look at something like: Redmon

This can take the output and spawn an new process. The idea would be that you have it output the Postscript to a file and then you launch some console .exe that you create against it.

Just a thought.

Again not sure which way round you are doing this, but ghostscript is the simplest way to convert a PS output into any other format. It's also pretty easy to write your own output format for ghostscript.

This all happens at the app level - no need to write a driver.