帮助正确计算atan2
-
28-09-2019 - |
题
我需要计算线之间的角度。我需要计算Atan。所以我正在使用这样的代码
static inline CGFloat angleBetweenLinesInRadians2(CGPoint line1Start, CGPoint line1End)
{
CGFloat dx = 0, dy = 0;
dx = line1End.x - line1Start.x;
dy = line1End.y - line1Start.y;
NSLog(@"\ndx = %f\ndy = %f", dx, dy);
CGFloat rads = fabs(atan2(dy, dx));
return rads;
}
但是我不能超过180度((179度后178..160..150之后,依此类推。
我需要在360度上旋转。我该怎么做?怎么了?
Maby这有帮助:
//Tells the receiver when one or more fingers associated with an event move within a view or window.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
NSArray *Touches = [touches allObjects];
UITouch *first = [Touches objectAtIndex:0];
CGPoint b = [first previousLocationInView:[self imgView]]; //prewious position
CGPoint c = [first locationInView:[self imgView]]; //current position
CGFloat rad1 = angleBetweenLinesInRadians2(center, b); //first angel
CGFloat rad2 = angleBetweenLinesInRadians2(center, c); //second angel
CGFloat radAngle = fabs(rad2 - rad1); //angel between two lines
if (tempCount <= gradus)
{
[imgView setTransform: CGAffineTransformRotate([imgView transform], radAngle)];
tempCount += radAngle;
}
}
解决方案
去除那个 fabs
致电并简单地做到:
CGFloat rads = atan2(dy, dx);
其他提示
atan2
返回结果[-180,180](弧度为-pi,pi)。从0,360获取结果:
float radians = atan2(dy, dx);
if (radians < 0) {
radians += M_PI*2.0f;
}
应该注意的是,在[-pi,pi]中表达旋转是典型的 atan2
不用担心标志。
在Swift中使用此功能。这确保从“从”到“ topoint”的角度在0到<360(不包括360)之间。请注意,以下功能假设CGPONTZERO在左上角。
func getAngle(fromPoint: CGPoint, toPoint: CGPoint) -> CGFloat {
let dx: CGFloat = fromPoint.x - toPoint.x
let dy: CGFloat = fromPoint.y - toPoint.y
let twoPi: CGFloat = 2 * CGFloat(M_PI)
let radians: CGFloat = (atan2(dy, -dx) + twoPi) % twoPi
return radians * 360 / twoPi
}
对于原点位于左下角的情况
let twoPi = 2 * Float(M_PI)
let radians = (atan2(-dy, -dx) + twoPi) % twoPi
let angle = radians * 360 / twoPi
不隶属于 StackOverflow