Process Image Data in any orientation and make a UIImage in an "up" orientation

gistfile1.txt

// Based on https://gist.github.com/schickling/b5d86cb070130f80bb40#gistcomment-2894406
func image(data: Data, orientation: UIImage.Orientation = .up) -> UIImage? {
    let context: CGContext
    let width: CGFloat
    let height: CGFloat

    func defaultImage() -> UIImage? {
        return UIImage(data: data)
    }

    do {
        guard
            let imageSource = CGImageSourceCreateWithData(data as CFData, nil),
            let properties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, nil) as NSDictionary?,
            let orientation = CGImagePropertyOrientation(rawValue: properties[kCGImagePropertyOrientation] as? UInt32 ?? 1),
            let image = CGImageSourceCreateImageAtIndex(imageSource, 0, nil)
        else { return defaultImage() }

        guard orientation != .up else { return UIImage(cgImage: image) }
        let imageOrientation = UIImage.Orientation(orientation)

        let bytesPerRow: Int
        switch imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            width = CGFloat(image.height)
            height = CGFloat(image.width)
            bytesPerRow = ((Int(width)+15)/16) * 16 * (image.bitsPerPixel/8)
        default:
            width = CGFloat(image.width)
            height = CGFloat(image.height)
            bytesPerRow = image.bytesPerRow
        }

        guard let _context = CGContext(data: nil,
                                       width: Int(width),
                                       height: Int(height),
                                       bitsPerComponent: image.bitsPerComponent,
                                       bytesPerRow: bytesPerRow,
                                       space: image.colorSpace ?? CGColorSpace(name: CGColorSpace.sRGB)!,
                                       bitmapInfo: image.bitmapInfo.rawValue)
        else { return defaultImage() }
        context = _context

        let drawRect: CGRect
        var transform: CGAffineTransform = CGAffineTransform.identity

        switch imageOrientation {
        case .down, .downMirrored:
            transform = transform.translatedBy(x: width, y: height)
            transform = transform.rotated(by: CGFloat.pi)
        case .left, .leftMirrored:
            transform = transform.translatedBy(x: width, y: 0)
            transform = transform.rotated(by: CGFloat.pi / 2.0)
        case .right, .rightMirrored:
            transform = transform.translatedBy(x: 0, y: 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: width, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .leftMirrored, .rightMirrored:
            transform = transform.translatedBy(x: height, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .up, .down, .left, .right:
            break
        @unknown default:
            break
        }

        context.concatenate(transform)

        switch imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            drawRect = CGRect(x: 0, y: 0, width: height, height: width)
        default:
            drawRect = CGRect(x: 0, y: 0, width: width, height: height)
        }

        context.draw(image, in: drawRect)
        // image released
    }

    guard let newImage = context.makeImage() else { return defaultImage() }

    let uiImage = UIImage(cgImage: newImage, scale: 1, orientation: .up)
    return uiImage
}

I recently tripped on this CIImage filter (new in iOS11):

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 than the above code.