Extension to fix orientation of an UIImage (Sets orientation to portrait)

UIImageFixedOrientationExtension.swift

extension UIImage {

    func fixedOrientation() -> UIImage {
        
        if imageOrientation == UIImageOrientation.Up {
            return self
        }
        
        var transform: CGAffineTransform = CGAffineTransformIdentity
        
        switch imageOrientation {
        case UIImageOrientation.Down, UIImageOrientation.DownMirrored:
            transform = CGAffineTransformTranslate(transform, size.width, size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI))
            break
        case UIImageOrientation.Left, UIImageOrientation.LeftMirrored:
            transform = CGAffineTransformTranslate(transform, size.width, 0)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI_2))
            break
        case UIImageOrientation.Right, UIImageOrientation.RightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(-M_PI_2))
            break
        case UIImageOrientation.Up, UIImageOrientation.UpMirrored:
            break
        }
        
        switch imageOrientation {
        case UIImageOrientation.UpMirrored, UIImageOrientation.DownMirrored:
            CGAffineTransformTranslate(transform, size.width, 0)
            CGAffineTransformScale(transform, -1, 1)
            break
        case UIImageOrientation.LeftMirrored, UIImageOrientation.RightMirrored:
            CGAffineTransformTranslate(transform, size.height, 0)
            CGAffineTransformScale(transform, -1, 1)
        case UIImageOrientation.Up, UIImageOrientation.Down, UIImageOrientation.Left, UIImageOrientation.Right:
            break
        }
        
        let ctx: CGContextRef = CGBitmapContextCreate(nil, Int(size.width), Int(size.height), CGImageGetBitsPerComponent(CGImage), 0, CGImageGetColorSpace(CGImage), CGImageAlphaInfo.PremultipliedLast.rawValue)!
        
        CGContextConcatCTM(ctx, transform)
        
        switch imageOrientation {
        case UIImageOrientation.Left, UIImageOrientation.LeftMirrored, UIImageOrientation.Right, UIImageOrientation.RightMirrored:
            CGContextDrawImage(ctx, CGRectMake(0, 0, size.height, size.width), CGImage)
            break
        default:
            CGContextDrawImage(ctx, CGRectMake(0, 0, size.width, size.height), CGImage)
            break
        }
        
        let cgImage: CGImageRef = CGBitmapContextCreateImage(ctx)!
        
        return UIImage(CGImage: cgImage)
    }
}

Gosh, this works amazingly, but seems to cause a memory crash for me half the time. Just calling it once. Even after adding return autoreleasepool {} around it as suggested by @peterdk.

@rubencodes
I also saw memory spikes. I first tried just keeping around a large enough memory blog to use with CGContext so it wouldn't have to keep creating one. That helped the smiles but the floor of memory usage rose (of course). Then I tripped on this CIImage filter (new in iOS11):

//image is a UIImage
let newImage = origImage.oriented(CGImagePropertyOrientation(image.imageOrientation))
guard let cgImage = context.createCGImage(newImage, from: newImage.extent) else { fatalError() }
let showImage = UIImage(cgImage: cgImage)

It creates much smaller memory spikes.

Swift 5

This version resolves memory spike as suggested by @peterdk.

extension UIImage {

    static func fixedOrientation(for image: UIImage) -> UIImage? {
        
        guard image.imageOrientation != .up else {
            return image
        }
        
        let size = image.size
        
        let imageOrientation = image.imageOrientation
        
        var transform: CGAffineTransform = .identity

        switch image.imageOrientation {
        case .down, .downMirrored:
            transform = transform.translatedBy(x: size.width, y: size.height)
            transform = transform.rotated(by: CGFloat.pi)
        case .left, .leftMirrored:
            transform = transform.translatedBy(x: size.width, y: 0)
            transform = transform.rotated(by: CGFloat.pi / 2.0)
        case .right, .rightMirrored:
            transform = transform.translatedBy(x: 0, y: size.height)
            transform = transform.rotated(by: CGFloat.pi / -2.0)
        case .up, .upMirrored:
            break
        @unknown default:
            break
        }

        // Flip image one more time if needed to, this is to prevent flipped image
        switch imageOrientation {
        case .upMirrored, .downMirrored:
            transform = transform.translatedBy(x: size.width, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .leftMirrored, .rightMirrored:
            transform = transform.translatedBy(x: size.height, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .up, .down, .left, .right:
            break
        @unknown default:
            break
        }
        
        guard var cgImage = image.cgImage else {
            return nil
        }
        
        autoreleasepool {
            var context: CGContext?
            
            guard let colorSpace = cgImage.colorSpace, let _context = CGContext(data: nil, width: Int(image.size.width), height: Int(image.size.height), bitsPerComponent: cgImage.bitsPerComponent, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
                return
            }
            context = _context
            
            context?.concatenate(transform)

            var drawRect: CGRect = .zero
            switch imageOrientation {
            case .left, .leftMirrored, .right, .rightMirrored:
                drawRect.size = CGSize(width: size.height, height: size.width)
            default:
                drawRect.size = CGSize(width: size.width, height: size.height)
            }

            context?.draw(cgImage, in: drawRect)
            
            guard let newCGImage = context?.makeImage() else {
                return
            }
            cgImage = newCGImage
        }
        
        let uiImage = UIImage(cgImage: cgImage, scale: 1, orientation: .up)
        return uiImage
    }
}

What about when the image is taken with frontal camera (selfie)? This does not work.

Great!

Nice!
Thanks all

Hi, here's my solution. It relies on iOS's UIImage handing of the orientation.
So an "xyz" orientated image is rendered (using it's orientation info) onto an up orientated canvas.

⚠️ self.draw of UIImage, not CGImage.

extension UIImage
{
    /// `Re-orientate` the image to `up`.
    ///
    func normalizedImage() -> UIImage?
    {
        if self.imageOrientation == .up
        {
            return self
        }
        else
        {
            UIGraphicsBeginImageContextWithOptions(self.size, false, self.scale)
            defer
            {
                UIGraphicsEndImageContext()
            }

            self.draw(in: CGRect(origin: .zero, size: self.size))

            return UIGraphicsGetImageFromCurrentImageContext()
        }
    }
}

Its saved my time! Thanks all !!!

Amazing. Great work buds.

Could someone explain me why we need transform.translatedBy?

Wouldn't only .rotated(by... and .scaledBy(... (for flipped images) do it? 🤔

I believe those transform around the origin (0, 0) and would thus flip/rotate your image to be outside the box. if you try it with an angle of around 45° you’ll see how it would break.

I believe those transform around the origin (0, 0) and would thus flip/rotate your image to be outside the box. if you try it with an angle of around 45° you’ll see how it would break.

Thanks!