iOS Swift 检测图像旋转 [英] iOS Swift Detecting Image Rotation

问题描述

我有一个应用程序，只要用户按下屏幕，它就会为仪表上的指针设置动画.当手指抬起时，我需要知道针的旋转角度.手指一抬起，我就删除了所有动画，但我不知道如何获得针的当前旋转角度.

I have an app which animates a needle on a meter as long as the user is pressing on the screen. When the finger is lifted I need to know the rotation angle of the needle. I remove all animations as soon as the finger is lifted but I can't figure how to get the current rotation angle of the needle.

推荐答案

很简单，这是完整的解决方案:

It is quite simple, this is the full solution:

示例设置:

imageView.transform = CGAffineTransform(rotationAngle: CGFloat.pi / 6) // just to test (it is 30 in degrees and 0.523598775598299 in radians)

代码:

let rad: Double = atan2( Double(imageView.transform.b), Double(imageView.transform.a))
let deg: CGFloat = CGFloat(rad) * (CGFloat(180) / CGFloat.pi )
print(deg) // works, printing 30

其中 deg = 度数 和 rad = 弧度

说明:第一行是获取弧度，第二行是将弧度乘以弧度的等价物，得到度数.

Explanation: The first line is getting the radians, and the second line is multiplying the radians by the equivalent of a radian in degrees, to get the degrees.

注意:

1. 在CGAffineTransform(rotationAngle: someValue)中，someValue实际上是角度的弧度，不是以度数来衡量的.有关以下内容的更多信息:

1. In CGAffineTransform(rotationAngle: someValue), someValue is, in fact, the radians of the angle, it is not measured in degrees. More information about:

• 弧度

度

PI

弧度值CGFloat.pi 是 180，因此您可以根据此测试任何角度.

The value in degrees of the radian CGFloat.pi is 180, therefore you can test it for any angle depending on this.

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让我知道这是否有帮助！

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Let me know if this helps!

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