Re: Cocoa and PICT
Re: Cocoa and PICT
- Subject: Re: Cocoa and PICT
- From: Scott Thompson <email@hidden>
- Date: Fri, 10 Aug 2007 16:57:28 -0500
On Aug 10, 2007, at 4:25 PM, Alastair Houghton wrote:
On 10 Aug 2007, at 14:51, glenn andreas wrote:
There's even support for smoothing polygons using picture
comments, which might be handy for simulating bezier paths.
Quickdraw pic comment based smooth polygons are cubics, and bezier
paths are quadratic curves, and converting from one to the other is
non-trivial (for any sort of decent quality).
I think you got that the wrong way round. QuickDraw PolySmooth
picture comment uses quadratic curves; NSBezierPath provides a cubic
primitive. (Plainly you knew what you meant, since converting
quadratic curves to cubics is easy... it's the other way that
requires piecewise approximation.)
Kind regards,
Alastair.
Well, if we're going to pick on Glenn :-)
It's also the case that the cubic and quadratic curves are both Bezier
curves. So the more accurate statement might be that "QuickDraw's
pic comment based smooth polygons are quadratic bezier curves" while
"NSBezierPath are based on cubic bezier curves".
It's interesting to note, however, that the Core Graphics library that
lies underneath NSBezierPath has direct support for quadratic bezier
curves. See CGContextAddQuadCurveToPoint
In Tiger It's not too hard to put some Quartz 2D calls in the midst of
your NSBezierPath-and-friends drawing so if you REALLY wanted to parse
the PICT comments and draw quadratic curves, you could probably do it
without too much trouble.
Scott
P.S. Blast from the past : http://www.mactech.com/articles/mactech/Vol.04/04.12/PicComments/index.html
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