How can I rotate an UIImageView by 20 degrees?

问题:

What do I have to do, if I need to rotate a UIImageView? I have a UIImage which I want to rotate by 20 degrees.

The Apple docs talk about a transformation matrix, but that sounds difficult. Are there any helpful methods or functions to achieve that?

回答1:

A transformation matrix is not incredibly difficult. It's quite simple, if you use the supplied functions:

imgView.transform = CGAffineTransformMakeRotation(.34906585);

(.34906585 is 20 degrees in radians)

---

Swift 5:

imgView.transform = CGAffineTransform(rotationAngle: .34906585)

回答2:

If you want to turn right, the value must be greater than 0 if you want to rotate to the left indicates the value with the sign "-". For example -20.

CGFloat degrees = 20.0f; //the value in degrees
CGFloat radians = degrees * M_PI/180;
imageView.transform = CGAffineTransformMakeRotation(radians);

Swift 4:

let degrees: CGFloat = 20.0 //the value in degrees
let radians: CGFloat = degrees * (.pi / 180)
imageView.transform = CGAffineTransform(rotationAngle: radians)

回答3:

Swift version:

let degrees:CGFloat = 20
myImageView.transform = CGAffineTransformMakeRotation(degrees * CGFloat(M_PI/180) )

回答4:

Swift 4.0

imageView.transform = CGAffineTransform(rotationAngle: CGFloat(20.0 * Double.pi / 180))

回答5:

Here's an extension for Swift 3.

extension UIImageView {

    func rotate(degrees:CGFloat){
        self.transform = CGAffineTransform(rotationAngle: degrees * CGFloat(M_PI/180))
      }  
    }

Usage:

myImageView.rotate(degrees: 20)

回答6:

_YourImageView.transform = CGAffineTransformMakeRotation(1.57);

where 1.57 is the radian value for 90 degree

回答7:

This is an easier formatting example (for 20 degrees):

CGAffineTransform(rotationAngle: ((20.0 * CGFloat(M_PI)) / 180.0))

回答8:

As far as I know, using the matrix in UIAffineTransform is the only way to achieve a rotation without the help of a third-party framework.