Replacing UIImageJPEGRepresentation with UIGraphicsImageRenderer's jpegData

I am working to add support for wide color photos in iOS 10. When the user takes a photo from the camera, I need to use the new API that supports the new color space to save the photo data - UIGraphicsImageRenderer's jpegData instead of UIImageJPEGRepresentation.

I'm running into some troubles with image orientations. Taking a photo on my iPad in portrait, the image isn't being drawn correctly. See the comments below:

Old API:

let image = info[UIImagePickerControllerOriginalImage] as! UIImage
let imageData = UIImageJPEGRepresentation(image, 1)

New API:

let image = info[UIImagePickerControllerOriginalImage] as! UIImage
let cgImage = image.cgImage!
let ciImage = CIImage(cgImage: cgImage)

let format = UIGraphicsImageRendererFormat()
format.scale = 1
format.prefersExtendedRange = true

let renderer = UIGraphicsImageRenderer(bounds: ciImage.extent, format: format)
let imageData = renderer.jpegData(withCompressionQuality: 1, actions: { context in
    context.cgContext.draw(cgImage, in: ciImage.extent) //draws flipped horizontally
    //image.draw(at: .zero) //draws rotated 90 degrees leaving black at bottom
    //image.draw(in: ciImage.extent) //draws rotated 90 degrees stretching and compressing the image to fill the rect 
 })

What's the correct way to replace UIImageJPEGRepresentation with UIGraphicsImageRenderer's jpegData?

Solution

UIImage can have different orientation depending on camera rotation. You can dynamically resolve the transformation needed to be applied to the image depending on that orientation, like this:

let renderer = UIGraphicsImageRenderer(size: image.size, format: format)
let imageData = renderer.jpegData(withCompressionQuality: 1, actions: { context in
    var workSize = image.size;
    workSize.width = floor(workSize.width / image.scale)
    workSize.height = floor(workSize.height / image.scale)
    // No-op if the orientation is already correct
    // if image.imageOrientation == .up { draw image }

    // We need to calculate the proper transformation to make the image upright.
    // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.

    var transform = CGAffineTransform.identity

    switch image.imageOrientation
    {
        case .down, .downMirrored:
            transform = transform.translatedBy(x: workSize.width, y: workSize.height)
            transform = transform.rotated(by: CGFloat(Double.pi))
            break

        case .left, .leftMirrored:
            transform = transform.translatedBy(x: workSize.width, y: 0.0)
            transform = transform.rotated(by: CGFloat(Double.pi / 2.0))
            break

        case .right, .rightMirrored:
            transform = transform.translatedBy(x: 0.0, y: workSize.height)
            transform = transform.rotated(by: CGFloat(-Double.pi / 2.0))
            break

        case .up, .upMirrored:
            break
    }

    switch image.imageOrientation
    {
        case .upMirrored, .downMirrored:
            transform = transform.translatedBy(x: workSize.width, y: 0.0)
            transform = transform.scaledBy(x: -1.0, y: 1.0)
            break

        case .leftMirrored, .rightMirrored:
            transform = transform.translatedBy(x: workSize.height, y: 0.0);
            transform = transform.scaledBy(x: -1.0, y: 1.0);
            break

        case .up, .down, .left, .right:
            break
    }

    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.

    let ctx = context.cgContext

    ctx.concatenate(transform)

    switch image.imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            ctx.draw(image.cgImage!, in: CGRect(x: 0.0, y:0.0, width: workSize.height, height: workSize.width))
            break;

        default:
            ctx.draw(image.cgImage!, in: CGRect(origin: .zero, size: workSize))
            break;
    } 
 })

Answer based on UIImage+fixOrientation