Scale and orient UIImage coming from image picker (according to apple sample)

orientation.swift

func scaleAndOrient(image: UIImage) -> UIImage {
        
        // Set a default value for limiting image size.
        let maxResolution: CGFloat = 640
        
        guard let cgImage = image.cgImage else {
            print("UIImage has no CGImage backing it!")
            return image
        }
        
        // Compute parameters for transform.
        let width = CGFloat(cgImage.width)
        let height = CGFloat(cgImage.height)
        var transform = CGAffineTransform.identity
        
        var bounds = CGRect(x: 0, y: 0, width: width, height: height)
        
        if width > maxResolution ||
            height > maxResolution {
            let ratio = width / height
            if width > height {
                bounds.size.width = maxResolution
                bounds.size.height = round(maxResolution / ratio)
            } else {
                bounds.size.width = round(maxResolution * ratio)
                bounds.size.height = maxResolution
            }
        }
        
        let scaleRatio = bounds.size.width / width
        let orientation = image.imageOrientation
        switch orientation {
        case .up:
            transform = .identity
        case .down:
            transform = CGAffineTransform(translationX: width, y: height).rotated(by: .pi)
        case .left:
            let boundsHeight = bounds.size.height
            bounds.size.height = bounds.size.width
            bounds.size.width = boundsHeight
            transform = CGAffineTransform(translationX: 0, y: width).rotated(by: 3.0 * .pi / 2.0)
        case .right:
            let boundsHeight = bounds.size.height
            bounds.size.height = bounds.size.width
            bounds.size.width = boundsHeight
            transform = CGAffineTransform(translationX: height, y: 0).rotated(by: .pi / 2.0)
        case .upMirrored:
            transform = CGAffineTransform(translationX: width, y: 0).scaledBy(x: -1, y: 1)
        case .downMirrored:
            transform = CGAffineTransform(translationX: 0, y: height).scaledBy(x: 1, y: -1)
        case .leftMirrored:
            let boundsHeight = bounds.size.height
            bounds.size.height = bounds.size.width
            bounds.size.width = boundsHeight
            transform = CGAffineTransform(translationX: height, y: width).scaledBy(x: -1, y: 1).rotated(by: 3.0 * .pi / 2.0)
        case .rightMirrored:
            let boundsHeight = bounds.size.height
            bounds.size.height = bounds.size.width
            bounds.size.width = boundsHeight
            transform = CGAffineTransform(scaleX: -1, y: 1).rotated(by: .pi / 2.0)
        }