Re: Calculating accurate bounds of stroked paths
Re: Calculating accurate bounds of stroked paths
- Subject: Re: Calculating accurate bounds of stroked paths
- From: Chris Suter <email@hidden>
- Date: Wed, 9 Jul 2008 16:02:51 +1000
Hi Graham,
On 08/07/2008, at 10:16 PM, Graham Cox wrote:
A close second best would be a rect that was the worst case bounds
for a given stroke width (it wouldn't need to know the actual path,
just its basic bounds), which thus assumed that all angles were
acute enough to trigger the mitre conversion. Even that is proving
hard to figure, as I'm probably not really understand the miter
limit calculation. The docs state:
Well, the miter limit is simply the point at which the join is
converted to a bevel join and a bevel join will always have a smaller
bounding box than a mitre join so you can get a worst case bounds by
ignoring the mitre limit.
"The miter limit helps you avoid spikes at the junction of two line
segments connected by a miter join (NSMiterLineJoinStyle). If the
ratio of the miter length—the diagonal length of the miter join—to
the line thickness exceeds the miter limit, the joint is converted
to a bevel join. The default miter limit value is 10, which converts
miters whose angle at the joint is less than 11 degrees."
So what *is it*? A value in degrees? Or a ratio of two sides of a
triangle? What triangle, exactly? How can I tell just how far out I
need to outset the rect to make sure I'm always just outside the
edge of any mitred corner?
You should have a look at the PDF specification (you can easily get
hold of it). It explains exactly what it is.
-- Chris
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