iOS - UIImageView - how to handle UIImage image orientation

You can completely avoid manually doing the transforms and scaling yourself, as suggested by an0 in this answer here:

- (UIImage *)normalizedImage {
    if (self.imageOrientation == UIImageOrientationUp) return self; 

    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    [self drawInRect:(CGRect){0, 0, self.size}];
    UIImage *normalizedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return normalizedImage;
}

The documentation for the UIImage methods size and drawInRect explicitly states that they take into account orientation.

This method first checks the current orientation of UIImage and then it changes the orientation in a clockwise way and return UIImage.You can show this image as

self.imageView.image = rotateImage(currentUIImage)

   func rotateImage(image:UIImage)->UIImage
    {
        var rotatedImage = UIImage();
        switch image.imageOrientation
        {
            case UIImageOrientation.Right:
            rotatedImage = UIImage(CGImage:image.CGImage!, scale: 1, orientation:UIImageOrientation.Down);
            
           case UIImageOrientation.Down:
            rotatedImage = UIImage(CGImage:image.CGImage!, scale: 1, orientation:UIImageOrientation.Left);
            
            case UIImageOrientation.Left:
            rotatedImage = UIImage(CGImage:image.CGImage!, scale: 1, orientation:UIImageOrientation.Up);
    
             default:
            rotatedImage = UIImage(CGImage:image.CGImage!, scale: 1, orientation:UIImageOrientation.Right);
        }
        return rotatedImage;
    }

Swift 4 version

extension UIImage {

func rotate() -> UIImage {
    var rotatedImage = UIImage()
    guard let cgImage = cgImage else {
        print("could not rotate image")
        return self
    }
    switch imageOrientation {
    case .right:
        rotatedImage = UIImage(cgImage: cgImage, scale: scale, orientation: .down)
    case .down:
        rotatedImage = UIImage(cgImage: cgImage, scale: scale, orientation: .left)
    case .left:
        rotatedImage = UIImage(cgImage: cgImage, scale: scale, orientation: .up)
    default:
        rotatedImage = UIImage(cgImage: cgImage, scale: scale, orientation: .right)
    }
    
    return rotatedImage
}
}

Swift 3.1

func fixImageOrientation(_ image: UIImage)->UIImage {
    UIGraphicsBeginImageContext(image.size)
    image.draw(at: .zero)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage ?? image
}

If I understand, what you want to do is disregard the orientation of the UIImage? If so then you could do this:

UIImage *originalImage = [... whatever ...];

UIImage *imageToDisplay =
     [UIImage imageWithCGImage:[originalImage CGImage]
              scale:[originalImage scale]
              orientation: UIImageOrientationUp];

So you're creating a new UIImage with the same pixel data as the original (referenced via its CGImage property) but you're specifying an orientation that doesn't rotate the data.