Print Imaging Systems(IM:XP)

Inside Macintosh: QuickDraw GX Printing Extensions and Drivers /: Chapter 1 - Introduction to Printing Extensions and Drivers / About QuickDraw GX Printing Extensions and Printer Drivers

Print Imaging Systems
Some of the printing messages that QuickDraw GX sends are specific to the print imaging system that a printing device uses. A print imaging system is a part of the QuickDraw GX printing software that manages the conversion of QuickDraw GX shapes into data for a specific type of output device, such as a printer. QuickDraw GX supports four print imaging systems for printing documents, as shown in Table 1-1.
Table 1-1 Print imaging systems that QuickDraw GX supports
Imaging system Explanation
Raster For use with a raster output device such as an ImageWriter printer. Raster bitmap data and escape sequences are sent to accomplish the printing of each page.
PostScriptª For use with a PostScript output device such as an Apple LaserWriter printer. PostScript printing instructions are sent to accomplish the printing of each page.
Vector For use with a vector output device that uses a plotting language such as HPGL. QuickDraw GX shapes are converted into vectors, and the vector data and pen information are sent to the device to accomplish the printing of each page.
Portable digital document For the creation of a portable digital document (PDD).
If you are writing a driver that creates portable digital documents for transportation to other types of computing systems, you specify that your driver works with the portable digital document (PDD) imaging system, which is described in Inside Macintosh: QuickDraw GX Environment and Utilities.

QuickDraw GX defines a few imaging messages for the raster and vector imaging systems and a large number of imaging messages for the PostScript imaging system.
For each message, QuickDraw GX provides a default implementation that performs the basic task for which the message is intended. You can override any of these messages to customize the behavior for your extension or driver. In the resources that you provide, you specify which imaging system your extension or driver uses and which messages you are overriding.
When you develop a printing extension, you can choose to make the extension available for any or all of the imaging systems, depending on what tasks the extension needs to perform. When you develop a printer driver, you specify the appropriate imaging system for that printer. For example, if you are writing a raster printer driver, you specify that your driver works with the raster imaging system. You can then use the raster package controls ('ropt') resource to define the escape sequences used for performing line feeds on the printer. You can also override the GXRasterLineFeed message to implement how a line feed is performed.
If you are writing a PostScript printer driver, you specify that your driver works with
the PostScript imaging system. You can then use the PostScript preferences ('pdip') resource to specify such things as which level of PostScript and which color space your driver supports. You can also override any of the numerous PostScript printing messages to exercise control over your device.

**Table 1-1 Print imaging systems that QuickDraw GX supports**
Imaging system	Explanation
Raster	For use with a raster output device such as an ImageWriter printer. Raster bitmap data and escape sequences are sent to accomplish the printing of each page.
PostScriptª	For use with a PostScript output device such as an Apple LaserWriter printer. PostScript printing instructions are sent to accomplish the printing of each page.
Vector	For use with a vector output device that uses a plotting language such as HPGL. QuickDraw GX shapes are converted into vectors, and the vector data and pen information are sent to the device to accomplish the printing of each page.
Portable digital document	For the creation of a portable digital document (PDD).
If you are writing a driver that creates portable digital documents for transportation to other types of computing systems, you specify that your driver works with the portable digital document (PDD) imaging system, which is described in Inside Macintosh: QuickDraw GX Environment and Utilities.