Get rotated rectangle UIView corners' coordina

Question

I'm trying to find a rotated rectangle UIView's four corners' coordinates.

I think one way I can do is to use recognizer.rotation, find the rotated angle then calculate the origins. But that requires some geometry calculation.

- (IBAction)handlePan:(UIRotationGestureRecognizer*)recognizer {
    NSLog(@"Rotation in degrees since last change: %f", [recognizer rotation] * (180 / M_PI));
    recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
    NSLog(@"%@",recognizer);

    recognizer.rotation = 0;
    NSLog(@"bound is %f and %f, frame is %f and %f, %f and %f.",recognizer.view.bounds.size.width,recognizer.view.bounds.size.height, recognizer.view.frame.size.width,recognizer.view.frame.size.height, recognizer.view.frame.origin.x, recognizer.view.frame.origin.y);
}

I'm just wondering if there are any other easier ways to get the coordinates? Thanks!

EDIT:

Looks like we have a great answer here(see answer below). I have managed to calculate the corners through a stupid way -- using rotation angle and geometry. It works but not easy and light. I'm sharing my code here just in case some one may want to use it(Even though I doubt it.)

    float r = 100;
    NSLog(@"radius is %f.",r);
    float AAngle = M_PI/3+self.rotatedAngle;
    float AY = recognizer.view.center.y - sin(AAngle)*r;
    float AX = recognizer.view.center.x - cos(AAngle)*r;
    self.pointPADA = CGPointMake(AX, AY);
    NSLog(@"View Center is (%f,%f)",recognizer.view.center.x,recognizer.view.center.y);
    NSLog(@"Point A has coordinate (%f,%f)",self.pointPADA.x,self.pointPADA.y);

    float BAngle = M_PI/3-self.rotatedAngle;
    float BY = recognizer.view.center.y - sin(BAngle)*r;
    float BX = recognizer.view.center.x + cos(BAngle)*r;
    self.pointPADB = CGPointMake(BX, BY);
    NSLog(@"Point B has coordinate (%f,%f)",BX,BY);

    float CY = recognizer.view.center.y + sin(AAngle)*r;
    float CX = recognizer.view.center.x + cos(AAngle)*r;
    self.pointPADC = CGPointMake(CX, CY);
    NSLog(@"Point C has coordinate (%f,%f)",CX,CY);

    float DY = recognizer.view.center.y + sin(BAngle)*r;
    float DX = recognizer.view.center.x - cos(BAngle)*r;
    self.pointPADD = CGPointMake(DX, DY);
    NSLog(@"Point D has coordinate (%f,%f)",DX,DY);

Answer 1

Here's my solution though I wonder if there's a more succinct way:

CGPoint originalCenter = CGPointApplyAffineTransform(theView.center,
    CGAffineTransformInvert(theView.transform));

CGPoint topLeft = originalCenter;
topLeft.x -= theView.bounds.size.width / 2;
topLeft.y -= theView.bounds.size.height / 2;
topLeft = CGPointApplyAffineTransform(topLeft, theView.transform);

CGPoint topRight = originalCenter;
topRight.x += theView.bounds.size.width / 2;
topRight.y -= theView.bounds.size.height / 2;
topRight = CGPointApplyAffineTransform(topRight, theView.transform);

CGPoint bottomLeft = originalCenter;
bottomLeft.x -= theView.bounds.size.width / 2;
bottomLeft.y += theView.bounds.size.height / 2;
bottomLeft = CGPointApplyAffineTransform(bottomLeft, theView.transform);

CGPoint bottomRight = originalCenter;
bottomRight.x += theView.bounds.size.width / 2;
bottomRight.y += theView.bounds.size.height / 2;
bottomRight = CGPointApplyAffineTransform(bottomRight, theView.transform);

Answer 2

Checked answer in Swift 3.1

struct ViewCorners {
    private var _topLeft:     CGPoint!
    private var _topRight:    CGPoint!
    private var _bottomLeft:  CGPoint!
    private var _bottomRight: CGPoint!

    var topLeft:     CGPoint { return _topLeft }
    var topRight:    CGPoint { return _topRight }
    var bottomLeft:  CGPoint { return _bottomLeft }
    var bottomRight: CGPoint { return _bottomRight }

    private let originalCenter: CGPoint
    private let transformedView: UIView

    private func pointWith(multipliedWidth: CGFloat, multipliedHeight: CGFloat) -> CGPoint {
        var x = originalCenter.x
        x += transformedView.bounds.width  / 2 * multipliedWidth

        var y = originalCenter.y
        y += transformedView.bounds.height / 2 * multipliedHeight

        var result = CGPoint(x: x, y: y).applying(transformedView.transform)
        result.x += transformedView.transform.tx
        result.y += transformedView.transform.ty

        return result
    }

    init(view: UIView) {
        transformedView = view
        originalCenter = view.center.applying(view.transform.inverted())

        _topLeft =     pointWith(multipliedWidth:-1, multipliedHeight:-1)
        _topRight =    pointWith(multipliedWidth: 1, multipliedHeight:-1)
        _bottomLeft =  pointWith(multipliedWidth:-1, multipliedHeight: 1)
        _bottomRight = pointWith(multipliedWidth: 1, multipliedHeight: 1)

    }
}