How to generate CGPoint-Array out of UIBezierPath (to touch-slide object along given path) [duplicate]

Question

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• Drag UIView around Shape Comprised of CGMutablePaths 1 answer

I have a UIBezierPath (curved like an '8', with only 4 points in it) and I need to make some kind of CGPoint-Array out of it. Any ideas? thanx!

edit:

I have my bezier initlialized like that

-(void) initBezier
{
    theBezierPath = [UIBezierPath bezierPath];    
    [theBezierPath moveToPoint:P(211.00, 31.00)];
    [theBezierPath addCurveToPoint:P(870.00, 191.00) controlPoint1:P(432.00, -11.00) controlPoint2:P(593.00, 209.00)];
    [theBezierPath addCurveToPoint:P(731.00, 28.00) controlPoint1:P(1061.95, 178.53) controlPoint2:P(944.69, 5.78)];
    [theBezierPath addCurveToPoint:P(189.00, 190.00) controlPoint1:P(529.00, 49.00) controlPoint2:P(450.00, 189.00)];
    [theBezierPath addCurveToPoint:P(211.00, 31.00) controlPoint1:P(-33.01, 190.85) controlPoint2:P(71.00, 37.00)];
}

and I animate an object on it with

anim = [CAKeyframeAnimation animationWithKeyPath:@"emitterPosition"];
anim.path = theBezierPath.CGPath;
anim.calculationMode = kCAAnimationCubicPaced;
anim.repeatCount = HUGE_VALF;
anim.duration = tme;

I want to animate the object on the path pixel by pixel (via touch-position). I want the object to "snap" a given coordinate of a touch to the nearest point on the curve so it touch-slides the object along the path.

Answer 1

Use the CGPathApply() function to iterate over all elements in a path. As one of the arguments, you have to specify a pointer to a function that will then be called for each path element. The path element data structure (of type CGPathElement) then contains the point(s) that describe it.

Use NSValue as a wrapper to add the points to an NSMutableArray.

Answer 2

Neither UIBezierPath nor CGPath provide a way to evaluate the points along an arbitrary Bezier path, or a way to find the nearest point on the path. You'll have to write that code yourself.

Fortunately, this is a very well-studied topic. This tutorial has a lot of useful information, to get you started. You're interested in "cubic" or "third-order" Bezier curves.