Mac OS X and PDF

OS X is the first operating system on the market that actually uses PDF technology within the operating system itself. Apple calls this technology ‘Quartz’. Quartz is a layer of software that runs on top of Darwin, the core (or kernel) of the Mac OS X operating system. It is responsible for the rendering of all 2D objects. Alongside Quartz, OpenGL takes care of handling 3D data (used in games like Quake or Unreal as well as professional 3D applications like Maya) and QuickTime handles multimedia stuff (movies, sound,…).

Quartz

Quartz replaces QuickDraw, which was used within earlier versions of MacOS. Within QuickDraw, the native file format was PICT. With Quartz, this now becomes PDF.

Quartz performs a number of tasks that include include:

• automatic PDF generation and save-as-PDF (disk and clipboard)
• conversion of PDF data to raster data or PostScript. The fact that Quartz can rasterize PDF files means that even cheap inkjet printers can output complex files. Gone are the days when only the screen preview of EPS-files was printed on non-PostScript printers.
• a consistent feature set for all printers
• automatic on-screen preview of graphics
• high-quality screen rendering

In short: Quartz implements a set of rules for describing how pictures and text are displayed and printed. Because Quartz uses the PDF drawing model for imaging, native applications can create and import PDFs without the need for outside programs. Even spool files sent to a printer are PDF data.

Some people have been wondering whether Apple pays licenses to Adobe for the technology used in Quartz. Here is what an Apple employer had to say about this: “The Quartz renderer and the PDF interpreter that Apple ships with Mac OS X are built with Apple code, with no external licenses, by Apple employees. Adobe just publishes a specification for how it’s supposed to function. This gives Apple considerably more flexibility with regard to what Quartz and the PDF interpreter can be used for.”

Adobe PDF versus Quartz PDF

Since Quartz uses PDF, one would assume that everything that is possible within a PDF file is also supported by Quartz. This is not the case. Quartz uses only some of the features of PDF, it is based on a subset of the full PDF specs.

These are some of the things that are used within both the official PDF specs and Quartz:

• the PDF imaging model
• Common color spaces: grayscale, RGB and CMYK
• Embedding of images (even though Quartz does not support masks)

And these are things that are feasible in PDF but that are not implemented in Quartz for Mac OS 10.3 (Panther):

• Annotations
• Forms
• Actions
• Digital signatures

In fact, one of the main differences between both systems is that the PDF specs are now at version 1.7 while Quartz uses specs that are somewhere between PDF 1.3 and 1.4.

The advantage of having a PDF-based OS

PDF-support within Mac OS X is a good thing. Using PDF as an internal file format increases the acceptance of PDF as a file format for exchanging data. Programmers use PDF in a number of interesting ways. Take the database program Filemaker as an example: the native OS X version of FileMaker Pro 5.5 allows users to import PDF documents as QuickTime movies that they can attach to records.
The actual implementation of PDF within Quartz offers acceptable results for use in a prepress environment. Apple could still improve things but OS X 10.3 as an operating system is the closest fit to prepress that you will find on the market. Even though the PDF viewer in OS X is not as powerful as Adobe reader, it is far faster and a worthy alternative.