addArc(center:radius:startAngle:endAngle:clockwise:)
Adds an arc of a circle to the current path, specified with a radius and angles.
Declaration
func addArc(center: CGPoint, radius: CGFloat, startAngle: CGFloat, endAngle: CGFloat, clockwise: Bool)Parameters
- center:
The center of the arc, in user space coordinates.
- radius:
The radius of the arc, in user space coordinates.
- startAngle:
The angle to the starting point of the arc, measured in radians from the positive x-axis.
- endAngle:
The angle to the end point of the arc, measured in radians from the positive x-axis.
- clockwise:
True to make a clockwise arc; False to make a counterclockwise arc.
Discussion
This method calculates starting and ending points using the radius and angles you specify, uses a sequence of cubic Bézier curves to approximate a segment of a circle between those points, and then appends those curves to the current path.
The clockwise parameter determines the direction in which the arc is created; the actual direction of the final path is dependent on the current transformation matrix of the graphics context. In a flipped coordinate system (the default for UIView drawing methods in iOS), specifying a clockwise arc results in a counterclockwise arc after the transformation is applied.
If the current path already contains a subpath, this method adds a line connecting the current point to the starting point of the arc. If the current path is empty, his method creates a new subpath whose starting point is the starting point of the arc. The ending point of the arc becomes the new current point of the path.