寻找最接近CGPoint的对象

下面的方法应该可以做到这一点。如果你发现里面有什么奇怪的东西,尽管指出。

- (CGFloat)distanceBetweenRect:(CGRect)rect andPoint:(CGPoint)point
{
    // first of all, we check if point is inside rect. If it is, distance is zero
    if (CGRectContainsPoint(rect, point)) return 0.f;

    // next we see which point in rect is closest to point
    CGPoint closest = rect.origin;
    if (rect.origin.x + rect.size.width < point.x)
        closest.x += rect.size.width; // point is far right of us
    else if (point.x > rect.origin.x) 
        closest.x = point.x; // point above or below us
    if (rect.origin.y + rect.size.height < point.y) 
        closest.y += rect.size.height; // point is far below us
    else if (point.y > rect.origin.y)
        closest.y = point.y; // point is straight left or right

    // we've got a closest point; now pythagorean theorem
    // distance^2 = [closest.x,y - closest.x,point.y]^2 + [closest.x,point.y - point.x,y]^2
    // i.e. [closest.y-point.y]^2 + [closest.x-point.x]^2
    CGFloat a = powf(closest.y-point.y, 2.f);
    CGFloat b = powf(closest.x-point.x, 2.f);
    return sqrtf(a + b);
}

CGPoint p = CGPointMake(12,12);

CGRect a = CGRectMake(5,5,10,10);
CGRect b = CGRectMake(13,11,10,10);
CGRect c = CGRectMake(50,1,10,10);
NSLog(@"distance p->a: %f", [self distanceBetweenRect:a andPoint:p]);
// 2010-08-24 13:36:39.506 app[4388:207] distance p->a: 0.000000
NSLog(@"distance p->b: %f", [self distanceBetweenRect:b andPoint:p]);
// 2010-08-24 13:38:03.149 app[4388:207] distance p->b: 1.000000
NSLog(@"distance p->c: %f", [self distanceBetweenRect:c andPoint:p]);
// 2010-08-24 13:39:52.148 app[4388:207] distance p->c: 38.013157

- (CGFloat)distanceBetweenPoint:(CGPoint)a andPoint:(CGPoint)b
{
    CGFloat a2 = powf(a.x-b.x, 2.f);
    CGFloat b2 = powf(a.y-b.y, 2.f);
    return sqrtf(a2 + b2)
}

Update:removed fabsf();-x^2与x^2相同,因此没有必要。

distanceBetweenPoint:andPoint: 方法也一样,为了完整性。

private func distanceToRect(rect: CGRect, fromPoint point: CGPoint) -> CGFloat {
    // if it's on the left then (rect.minX - point.x) > 0 and (point.x - rect.maxX) < 0
    // if it's on the right then (rect.minX - point.x) < 0 and (point.x - rect.maxX) > 0
    // if it's inside the rect then both of them < 0. 
    let dx = max(rect.minX - point.x, point.x - rect.maxX, 0)
    // same as dx
    let dy = max(rect.minY - point.y, point.y - rect.maxY, 0)
    // if one of them == 0 then the distance is the other one.
    if dx * dy == 0 {
        return max(dx, dy)
    } else {
        // both are > 0 then the distance is the hypotenuse
        return hypot(dx, dy)
    }
}

谢谢@cristian,

- (CGFloat)distanceToRect:(CGRect)rect fromPoint:(CGPoint)point
{
    CGFloat dx = MAX(0, MAX(CGRectGetMinX(rect) - point.x, point.x - CGRectGetMaxX(rect)));
    CGFloat dy = MAX(0, MAX(CGRectGetMinY(rect) - point.y, point.y - CGRectGetMaxY(rect)));

    if (dx * dy == 0)
    {
        return MAX(dx, dy);
    }
    else
    {
        return hypot(dx, dy);
    }
}

更短的 @克里斯蒂安

func distance(from rect: CGRect, to point: CGPoint) -> CGFloat {
  let dx = max(rect.minX - point.x, point.x - rect.maxX, 0)
  let dy = max(rect.minY - point.y, point.y - rect.maxY, 0)
  return dx * dy == 0 ? max(dx, dy) : hypot(dx, dy)
}

就我个人而言,我会将此作为CGPoint扩展来实现:

extension CGPoint {
    func distance(from rect: CGRect) -> CGFloat {
        let dx = max(rect.minX - x, x - rect.maxX, 0)
        let dy = max(rect.minY - y, y - rect.maxY, 0)
        return dx * dy == 0 ? max(dx, dy) : hypot(dx, dy)
    }
}

或者,也可以将其实现为CGRect扩展:

extension CGRect {
    func distance(from point: CGPoint) -> CGFloat {
        let dx = max(minX - point.x, point.x - maxX, 0)
        let dy = max(minY - point.y, point.y - maxY, 0)
        return dx * dy == 0 ? max(dx, dy) : hypot(dx, dy)
    }
}