Introduction to Quartz 2D for QuickDraw Programmers
Subject:   Size issues
Date:   2004-09-29 12:59:24
From:   maartensneep1
You write:
"A traditional typographic point is slightly more than 1/72 of an inch, but in the imaging model shared by Quartz 2D and PDF, a point is defined to be exactly 1/72 of an inch."

Actually the traditional typographic point is slightly less, 1/72.27 of an inch, at least according to the TeXBook, which has the point, and the big-point (1/72 of an inch). This small difference is the cause of much confusion in the TeX world (keep in mind that TeX is older than postscript).


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  • Size issues
    2004-09-29 13:20:36  easco [View]

    It really depends on whose defintion of a typographic "point" you take. You can read one persons account on the subject at the link:

    The history of the American POINT SYSTEM

    According to that article, at least, the European standard for a "point" is 0.0148" which is slightly larger than 1/72 of an inch.

    However the American Standard is listed as 0.0138" or 1/72.46 which is slightly smaller than the point you mention.

    Nevertheless you are correct in your assesment. I was thinking of the 72.27 figure and got the magnitude wrong when dividing.

    Perhaps the article would be more accurate to say that "Depending on the source, the definition of a typographic point can be slightly different from 1/72 of an inch but Quartz 2D adopts the PostScript convention which defines it to be exactly 1/72 of an inch". Which is really what's important to know in this context anyway.