How Can I Rotate A UIImage and Image Data By 90 Degrees

Question

I have a UIImageView that contains an image. At the minute the user can click to save the image within the UIImageView to disk.

I would like to make it so that the the

Answer 1

I have such code in my old app. But this code can be simplified because you have no need to rotate it on non-90 degrees angle.

Objective-C

@implementation UIImage (Rotation)

- (UIImage *)imageRotatedOnDegrees:(CGFloat)degrees
{
  // Follow ing code can only rotate images on 90, 180, 270.. degrees.
  CGFloat roundedDegrees = (CGFloat)(round(degrees / 90.0) * 90.0);
  BOOL sameOrientationType = ((NSInteger)roundedDegrees) % 180 == 0;
  CGFloat radians = M_PI * roundedDegrees / 180.0;
  CGSize newSize = sameOrientationType ? self.size : CGSizeMake(self.size.height, self.size.width);

  UIGraphicsBeginImageContext(newSize);
  CGContextRef ctx = UIGraphicsGetCurrentContext();
  CGImageRef cgImage = self.CGImage;
  if (ctx == NULL || cgImage == NULL) {
    UIGraphicsEndImageContext();
    return self;
  }

  CGContextTranslateCTM(ctx, newSize.width / 2.0, newSize.height / 2.0);
  CGContextRotateCTM(ctx, radians);
  CGContextScaleCTM(ctx, 1, -1);
  CGPoint origin = CGPointMake(-(self.size.width / 2.0), -(self.size.height / 2.0));
  CGRect rect = CGRectZero;
  rect.origin = origin;
  rect.size = self.size;
  CGContextDrawImage(ctx, rect, cgImage);
  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return image ?: self;
}

@end

Swift

extension UIImage {

  func imageRotated(on degrees: CGFloat) -> UIImage {
    // Following code can only rotate images on 90, 180, 270.. degrees.
    let degrees = round(degrees / 90) * 90
    let sameOrientationType = Int(degrees) % 180 == 0
    let radians = CGFloat.pi * degrees / CGFloat(180)
    let newSize = sameOrientationType ? size : CGSize(width: size.height, height: size.width)

    UIGraphicsBeginImageContext(newSize)
    defer {
      UIGraphicsEndImageContext()
    }

    guard let ctx = UIGraphicsGetCurrentContext(), let cgImage = cgImage else {
      return self
    }

    ctx.translateBy(x: newSize.width / 2, y: newSize.height / 2)
    ctx.rotate(by: radians)
    ctx.scaleBy(x: 1, y: -1)
    let origin = CGPoint(x: -(size.width / 2), y: -(size.height / 2))
    let rect = CGRect(origin: origin, size: size)
    ctx.draw(cgImage, in: rect)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    return image ?? self
  }

}