ios iphone sdk CGAffineTransform 获取对象的旋转角度
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原文地址: http://stackoverflow.com/questions/2051811/
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iphone sdk CGAffineTransform getting the angle of rotation of an object
提问by nathanjosiah
how do i calculate the angle of rotation for any given object (ie a uiimageview)?
我如何计算任何给定对象（即 uiimageview）的旋转角度？
回答by kennytm
Technically you can't, because the transform can include a skewoperation which turns the image into a parallelogram and the rotation angle isn't defined anymore.
从技术上讲，您不能，因为变换可以包括将图像变成平行四边形的倾斜操作，并且不再定义旋转角度。
Anyway, since the rotation matrix generates
无论如何，由于旋转矩阵生成
cos(x) sin(x) 0
-sin(x) cos(x) 0
0 0 1
You can recover the angle with
你可以恢复角度
return atan2(transform.b, transform.a);
回答by sch
You can easily get the angle of the rotation like this:
您可以像这样轻松获得旋转角度：
CGFloat angle = [(NSNumber *)[view valueForKeyPath:@"layer.transform.rotation.z"] floatValue];
For example:
例如：
view.transform = CGAffineTransformMakeRotation(0.02);
CGFloat angle = [(NSNumber *)[view valueForKeyPath:@"layer.transform.rotation.z"] floatValue];
NSLog(@"%f", angle); // 0.020000
From the documentation:
从文档：
Core Animation extends the key-value coding protocol to allow getting and setting of the common values of a layer's CATransform3D matrix through key paths. Table 4 describes the key paths for which a layer's transform and sublayerTransform properties are key-value coding and observing compliant
Core Animation 扩展了键值编码协议，允许通过键路径获取和设置层的 CATransform3D 矩阵的公共值。表 4 描述了层的 transform 和 sublayerTransform 属性是键值编码和观察兼容的关键路径
回答by leon
Or you can use acos and asin functions. You will get exactly the same result:
或者您可以使用 acos 和 asin 函数。你会得到完全相同的结果：
NSLog (@"%f %f %f", acos (MyView.transform.a), asin (MyView.transform.b), atan2(MyView.transform.b, MyView.transform.a) );
回答by Abhishek Bedi
You can try with this:
你可以试试这个：
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint newLocationPoint = [[touches anyObject] locationInView:self.superview];
int x = self.center.x;
int y = self.center.y;
float dx = newLocationPoint.x - x;
float dy = newLocationPoint.y - y;
double angle = atan2(-dx,dy);
self.layer.position = self.center;
self.layer.transform = CATransform3DMakeRotation(angle, 0, 0, 1);
NSLog(@"touchesMoved %f %f %d,%d %f,%f angle:%f",newLocationPoint.x,newLocationPoint.y,x,y,dx,dy,angle);
}
回答by Rendel
I know this is very old question but, if anyone like me faces with this problem using CALayers and CATransform3D, you can get angle with:
我知道这是一个非常古老的问题，但是，如果像我这样的人使用 CALayer 和 CATransform3D 遇到这个问题，您可以通过以下方式获得角度：
extension CATransform3D {
var xAxisAngle: CGFloat { get { return atan2(self.m23, self.m33) } }
var yAxisAngle: CGFloat { get { return atan2(self.m31, self.m11) } }
var zAxisAngle: CGFloat { get { return atan2(self.m12, self.m11) } }
}
