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> I'm just curious as to how products that run as PDF print > drivers work? Are > they Postscript interpreters that convert the PS output to > PDF? I will talk about Windows only, as the concept of "printer driver" varies wildly by operating system. Some are. Kind of. Actually the PostScript interpreter is Acrobat Distiller (if you use Acrobat), which isn't a printer driver at all, but does convert PostScript to PDF. Let's take the Distiller driver. (Called "Adobe PDF" in Acrobat 6.0, "Acrobat Distiller" in earlier versions). This is the standard Windows PostScript driver. Adobe install a custom port. What's a port? It's essentially the thing that talks to the connected printer. There's a port for each USB printer, and a port for a printer on a parallel cable. Programmers can create new ports that don't have to talk to real hardware. Ok, what does this port do? Not very much. It waits to be sent the print file (PostScript, remember). When it has the file, it sends it to Distiller. This makes a PDF. Most of the work is in providing the user interface. But that's not the only way. A Windows printer driver is a special piece of software that understands a whole lot of graphical instructions (called GDI). Like - draw a line in red, 1 inch long from here to there. Or, paint this bitmap. Or, write the word HELP! in the Helvetica font. And so on. There are a lot of different graphical instructions, perhaps hundreds, so writing a printer driver isn't the work of an afternoon. Bear in mind that for the Distiller driver, they didn't need to write a driver at all, just a port. But what if you did write a driver that understood GDI and converted all those drawing instructions into PDF? This can be done, and it is this method that the PDFWriter driver, included with Acrobat 1.0 to 5.05, used. Aandi To change your subscription: http://www.pdfzone.com/discussions/lists-pdfdev.html
