objective c - How to get a correctly rotated UIImage from an ALAssetRepresentation?

Question

I’m trying to get a correctly rotated UIImage from an ALAssetRepresentation using the fullScreenImage method. I have several testing photos shot in various device orientations; the photos show up correctly in the Photos app. The documentation for fullScreenImage says:

In iOS 5 and later, this method returns a fully cropped, rotated, and adjusted image—exactly as a user would see in Photos or in the image picker.

To create a correctly-rotated UIImage object from the CGImage, you use imageWithCGImage:scale:orientation: or initWithCGImage:scale:orientation:, passing the values of orientation and scale.

Given the docs, my code looks like this:

ALAssetRepresentation *rep = [asset defaultRepresentation];
UIImage *img = [UIImage
    imageWithCGImage:[rep fullScreenImage]
    scale:[rep scale]
    orientation:[rep orientation]];

But the resulting UIImage’s rotation is wrong. When I replace [rep orientation] with UIImageOrientationUp, the image is fine for all testing photos. Obviously I’m hesitating to stick with this “solution”, as it feels like a hack. What am I doing wrong?

Answer 1

ALAssetRepresentation *rep = [asset defaultRepresentation];
UIImage *img = [UIImage
? ? imageWithCGImage:[rep fullScreenImage]
? ? scale:[rep scale]
? ? orientation:UIImageOrientationUp];

Is correct as under iOS?5 the fullscreenimages is already rotated (so it’s always “up”). Under iOS?4 the behaviour is different. Please see Orientation does not behave correctly with Photo in ALAsset for a more in depth explanation.