/// 计算三点之间的角度 /// /// - Parameters: /// - p1: 点1 /// - p2: 点2(也是角度所在点) /// - p3: 点3 /// - Returns: 角度(180度制) func getAnglesWithThreePoints(p1:CGPoint,p2:CGPoint,p3:CGPoint) -> Double { let a = p1.x - p2.x let b = p1.y - p2.y let c = p3.x - p2.x let d = p3.y - p2.y let e = (a*c+b*d) let f = sqrt(a*a+b*b) let g = sqrt(c*c+d*d) let r = Double(acos(e/(f*g))) return (180*r/Double.pi) }
P2位置就是要计算的角度。
ps:这个坐标点是基于iOS上的,左上角为原点,所以直接获取点即可。