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Re: Appending CGPath to CGPath
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Re: Appending CGPath to CGPath


  • Subject: Re: Appending CGPath to CGPath
  • From: Graham Cox <email@hidden>
  • Date: Sat, 16 Apr 2011 17:32:07 +1000

On 16/04/2011, at 4:40 PM, Roland King wrote:

> Where I'm getting the most time spent is in CGPathAddArc(), and this particular shape has a lot of them. My assumption here is that CGPathAddArc, which takes two angles, is having to calculate a bunch of trig functions of those and figure out which bezier paths to add to approximate it. Once I have the path calculated once, yes to rotate and translate it I'll have to iterate over the points and multiply each of them by the transformation, but that's a quicker operation  than recalculating each one of those arcs all over again from basics.

Yes, calculating arc-to-bezier is quite complicated (I just implemented this for importing SVG 'A' commands). If the arcs have common angles but there are many of them you could re-use the calculated arc segment using transforms to speed that up.

For joining paths in the way you describe, you have to use CGPathApply.

--Graham


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References: 
 >Appending CGPath to CGPath (From: Roland King <email@hidden>)
 >Re: Appending CGPath to CGPath (From: Graham Cox <email@hidden>)
 >Re: Appending CGPath to CGPath (From: Roland King <email@hidden>)

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