Tuesday, May 13, 2008

Quartz to PDF, versus PS to PDF

I am ankle deep in Postscript code at my day job, so as a refresher I took an afternoon and hand encoded a business card for my wife, who is starting a side business arranging academic tours of China (for the Peking University Department of Philosophy and Religion). Obviously, most people would be better served creating a card in InDesign, or other vectored drawing editor, but this was a learning experience.


Here it is with the contact info scrubbed.



Postscript is not a friendly language, but it was simple enough creating a .ps file in my text editor—BBEdit—and just dragging and dropping the icon from the editor's title bar onto the OS X Preview application. Preview has the convenient feature of auto-magically converting Postscript files to PDF. Of course, compilation errors result in a cryptic failure dialog, but these were enough development tools for an afternoon's project. If I were to do this on a more regular basis, I'd compile a simple app which provided a message callback to the CGPSConverterCreate routine.


Consider how much easier it would be to create this file in Quartz, and how much better the output would look.

  • Font handling is hard in Postscript, even if you don't have to embed descriptions of your fonts. Thus my use of standard Postscript fonts Times and Helvetica.
  • Kerning is not automatic in Postscript. Yes, you can use kshow to manually set the spacing between pairs of characters. No, I'm not going to do that. Thus, the odd spacing between letters.
  • If this file had included characters from non-Roman languages, complications would arise as Postscript only allows 256 characters per font encoding, potentially requiring multiple font definitions per face. None of the free Unicode support in Core Text/Quartz.
  • I might have used a little transparency, but there's no such thing in Postscript.
  • Postscript is hard to read and maintain. The extra syntax needed to keep the parameter stack organized, distracts the eye away from the actual algorithm being described. Postscript is certainly more compact in the editor, by an order of magnitude, than a series of Quartz API calls but much of that compactness is wasted pushing, popping, dup'ing, and rolling the parameter stack. I mean, just look at it: [Update: changed ATSUI to Core Text]
    gsave
    basefont [9 0 0 9 0 0] makefont setfont
    (Nashua, NH 03061)
    dup
    stringwidth pop 2 div neg 0 rmoveto
    show
    grestore



The fact of the matter is that Apple has done a lot of heavy lifting for us either via proprietary extensions to PDF, or taking the extra effort of providing optimized support for font embedding. An afternoon spent trying to keep track of an unruly parameter stack was enough for me to appreciate how much power Quartz gives us, and how easy it is to call upon.
 
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