How to rotate image in Swift?

Question

I am unable to rotate the image by 90 degrees in swift. I have written below code but there is an error and doesn't compile

  func imageRotatedByDegrees(oldImage: UIImage, deg degrees: CGFloat) -> UIImage {      //Calculate the size of the rotated view's containing box for our drawing space     let rotatedViewBox: UIView = UIView(frame: CGRect(x: 0, y: 0, width: oldImage.size.width, height: oldImage.size.height))     let t: CGAffineTransform = CGAffineTransform(rotationAngle: degrees * CGFloat(M_PI / 180))     rotatedViewBox.transform = t     let rotatedSize: CGSize = rotatedViewBox.frame.size      //Create the bitmap context     UIGraphicsBeginImageContext(rotatedSize)     let bitmap: CGContext = UIGraphicsGetCurrentContext()!      //Move the origin to the middle of the image so we will rotate and scale around the center.     bitmap.translateBy(x: rotatedSize.width / 2, y: rotatedSize.height / 2)      //Rotate the image context     bitmap.rotate(by: (degrees * CGFloat(M_PI / 180)))      //Now, draw the rotated/scaled image into the context     bitmap.scaleBy(x: 1.0, y: -1.0)     bitmap.draw(oldImage, in:  CGRect(origin: (x: -oldImage.size.width / 2,  y: -oldImage.size.height / 2, width:  oldImage.size.width, height: oldImage.size.height), size: oldImage.cgImage))      let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()!     UIGraphicsEndImageContext()      return newImage    } 

below is the code i am not sure about

bitmap.draw(oldImage, in:  CGRect(origin: (x: -oldImage.size.width / 2,  y: -oldImage.size.height / 2, width:  oldImage.size.width, height: oldImage.size.height), size: oldImage.cgImage)) 

Answer 1

set ImageView image

ImageView.transform = ImageView.transform.rotated(by: CGFloat(M_PI_2)) 

Swift 5

ImageView.transform = ImageView.transform.rotated(by: .pi)        // 180˚  ImageView.transform = ImageView.transform.rotated(by: .pi / 2)    // 90˚  ImageView.transform = ImageView.transform.rotated(by: .pi * 1.5)  // 270˚ 

Answer 2

This is an extension of UIImage that targets Swift 4.0 and can rotate just the image without the need for a UIImageView. Tested successfully that the image was rotated, and not just had its exif data changed.

import UIKit  extension UIImage {     func rotate(radians: CGFloat) -> UIImage {         let rotatedSize = CGRect(origin: .zero, size: size)             .applying(CGAffineTransform(rotationAngle: CGFloat(radians)))             .integral.size         UIGraphicsBeginImageContext(rotatedSize)         if let context = UIGraphicsGetCurrentContext() {             let origin = CGPoint(x: rotatedSize.width / 2.0,                                  y: rotatedSize.height / 2.0)             context.translateBy(x: origin.x, y: origin.y)             context.rotate(by: radians)             draw(in: CGRect(x: -origin.y, y: -origin.x,                             width: size.width, height: size.height))             let rotatedImage = UIGraphicsGetImageFromCurrentImageContext()             UIGraphicsEndImageContext()              return rotatedImage ?? self         }          return self     } } 

To perform a 180 degree rotation, you can call it like this:

let rotatedImage = image.rotate(radians: .pi) 

If for whatever reason it fails to rotate, the original image will then be returned.