iphone - How to determine intersection of CGPaths

Question

My Question is something similar to this.

I have 2 CGPathRef and 1 will be moved by finger touch. I want to find that whether the 2 CGPathRef are intersected? That question was asked almost 2 years ago and I want to know whether something has been found in the mean time.

Answer 1

This is fairly old, but I found it looking for a similar solution, in my problem I wanted to find when a circle overlapped with a path (a special case of your question).

I solved this by using CGPathCreateCopyByStrokingPath to create a stroked version of the original path using the radius of the circle as the stroke width. If the center point of the circle overlaps the stroked path then the original path overlaps the circle.

BOOL CGPathIntersectsCircle(CGPathRef path, CGPoint center, CGFloat radius)
{
    CGPathRef fuzzyPath;
    fuzzyPath = CGPathCreateCopyByStrokingPath(path, NULL, radius,
                                               kCGLineCapRound,
                                               kCGLineJoinRound, 0.0);
    if (CGPathContainsPoint(fuzzyPath, NULL, center, NO))
    {
        CGPathRelease(fuzzyPath);
        return YES;
    }
    CGPathRelease(fuzzyPath);
    return NO;
}

Edit: A minor bug where the fuzzyPath was not released.