Rotating UIImage in Swift

I'm using Xcode 6.0.1 with Swift. I have a UIImage, and I would like to make another image using the old image as a source, with the new image being rotated in some way... say flipped vertically.

This question was already answered a few months ago. However, that solution doesn't work for me, even though the situation is identical.

When I have

var image = UIImage(CGImage: otherImage.CGImage, scale: 1.0, orientation: .DownMirrored)

Xcode complains that there's an "Extra argument 'scale' in call". After checking with the Apple documentation, this makes no sense, as that version of the initializer does take those three arguments. Leaving out the scale and orientation arguments does fix the problem, but prevents me from doing the rotation.

The only other reference to this that I can find is this guy, who had the same problem.

What do you think?

I do need this to run on this version of Xcode, so if there's an alternate way to perform the rotation (I haven't found one yet) that would be useful.

Solution 1:

Swift 5 Solution

I wrote Pixel SDK which offers a more powerful solution to this problem, otherwise here is the simplest solution:

extension UIImage {
    func rotate(radians: Float) -> UIImage? {
        var newSize = CGRect(origin: CGPoint.zero, size: self.size).applying(CGAffineTransform(rotationAngle: CGFloat(radians))).size
        // Trim off the extremely small float value to prevent core graphics from rounding it up
        newSize.width = floor(newSize.width)
        newSize.height = floor(newSize.height)

        UIGraphicsBeginImageContextWithOptions(newSize, false, self.scale)
        let context = UIGraphicsGetCurrentContext()!

        // Move origin to middle
        context.translateBy(x: newSize.width/2, y: newSize.height/2)
        // Rotate around middle
        context.rotate(by: CGFloat(radians))
        // Draw the image at its center
        self.draw(in: CGRect(x: -self.size.width/2, y: -self.size.height/2, width: self.size.width, height: self.size.height))

        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }
}

and to use this solution you can do the following

let image = UIImage(named: "image.png")!
let newImage = image.rotate(radians: .pi/2) // Rotate 90 degrees

Solution 2:

Here is a simple extension to UIImage:

//ImageRotation.swift

import UIKit

extension UIImage {  
    public func imageRotatedByDegrees(degrees: CGFloat, flip: Bool) -> UIImage {
        let radiansToDegrees: (CGFloat) -> CGFloat = {
            return $0 * (180.0 / CGFloat(M_PI))
        }
        let degreesToRadians: (CGFloat) -> CGFloat = {
            return $0 / 180.0 * CGFloat(M_PI)
        }

        // calculate the size of the rotated view's containing box for our drawing space
        let rotatedViewBox = UIView(frame: CGRect(origin: CGPointZero, size: size))
        let t = CGAffineTransformMakeRotation(degreesToRadians(degrees));
        rotatedViewBox.transform = t
        let rotatedSize = rotatedViewBox.frame.size

        // Create the bitmap context
        UIGraphicsBeginImageContext(rotatedSize)
        let bitmap = UIGraphicsGetCurrentContext()

        // Move the origin to the middle of the image so we will rotate and scale around the center.
        CGContextTranslateCTM(bitmap, rotatedSize.width / 2.0, rotatedSize.height / 2.0);

        //   // Rotate the image context
        CGContextRotateCTM(bitmap, degreesToRadians(degrees));

        // Now, draw the rotated/scaled image into the context
        var yFlip: CGFloat

        if(flip){
            yFlip = CGFloat(-1.0)
        } else {
            yFlip = CGFloat(1.0)
        }

        CGContextScaleCTM(bitmap, yFlip, -1.0)
        CGContextDrawImage(bitmap, CGRectMake(-size.width / 2, -size.height / 2, size.width, size.height), CGImage)

        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }
}

(Source)

Use it with:

rotatedPhoto = rotatedPhoto?.imageRotatedByDegrees(90, flip: false) 

The former will rotate an image and flip it if flip is set to true.