UIImage FixOrientation

gistfile1.cs

public static UIImage FixOrientation(this UIImage image)
{
    UIImage fixedImage = image;

    // No-op if the orientation is already correct
    if (image.Orientation == UIImageOrientation.Up) return 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.
    CGAffineTransform transform = CGAffineTransform.MakeIdentity();

    switch (image.Orientation) 
    {
        case UIImageOrientation.Down:
        case UIImageOrientation.DownMirrored:
            transform = CGAffineTransform.Translate(transform, image.Size.Width, image.Size.Height);
            transform = CGAffineTransform.Rotate(transform, (float)Math.PI);
            break;

        case UIImageOrientation.Left:
        case UIImageOrientation.LeftMirrored:
            transform = CGAffineTransform.Translate(transform, image.Size.Width, 0);
            transform = CGAffineTransform.Rotate(transform, (float)(Math.PI / 2));
            break;

        case UIImageOrientation.Right:
        case UIImageOrientation.RightMirrored:
            transform = CGAffineTransform.Translate(transform, 0, image.Size.Height);
            transform = CGAffineTransform.Rotate(transform, (float)(-Math.PI / 2));
            break;
        case UIImageOrientation.Up:
        case UIImageOrientation.UpMirrored:
            break;
    }

    switch (image.Orientation) 
    {
        case UIImageOrientation.UpMirrored:
        case UIImageOrientation.DownMirrored:
            transform = CGAffineTransform.Translate(transform, image.Size.Width, 0);
            transform = CGAffineTransform.Scale(transform, -1, 1);
            break;

        case UIImageOrientation.LeftMirrored:
        case UIImageOrientation.RightMirrored:
            transform = CGAffineTransform.Translate(transform, image.Size.Height, 0);
            transform = CGAffineTransform.Scale(transform, -1, 1);
            break;
        case UIImageOrientation.Up:
        case UIImageOrientation.Down:
        case UIImageOrientation.Left:
        case UIImageOrientation.Right:
            break;
    }

    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.
    using(var bitmapContext = new CGBitmapContext(IntPtr.Zero, (int)image.Size.Width, (int)image.Size.Height,
        image.CGImage.BitsPerComponent, 0,
        image.CGImage.ColorSpace,
        image.CGImage.BitmapInfo))
    {
        bitmapContext.ConcatCTM(transform);

        switch (image.Orientation) {
            case UIImageOrientation.Left:
            case UIImageOrientation.LeftMirrored:
            case UIImageOrientation.Right:
            case UIImageOrientation.RightMirrored:
                bitmapContext.DrawImage(new RectangleF(0,0,image.Size.Height,image.Size.Width), image.CGImage);
                break;

            default:
                bitmapContext.DrawImage(new RectangleF(0,0,image.Size.Width,image.Size.Height), image.CGImage);
                break;
        }

        // And now we just create a new UIImage from the drawing context
        using(var cgimg = bitmapContext.ToImage())
        {
            fixedImage = new UIImage(cgimg);
        }
    }

    return fixedImage;
}