Creating a UIImage from a rotated UIImageView...

Posted by Magic Bullet Dave on Stack Overflow See other posts from Stack Overflow or by Magic Bullet Dave
Published on 2010-05-18T11:00:29Z Indexed on 2010/05/21 6:50 UTC
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I have a UIImageView with an image in it. I have rotated the image prior to display by setting the transform property of the UIImageView to CGAffineTransformMakeRotation(angle) where angle is the angle in radians.

I want to be able to create another UIImage that corresponds to the rotated version that I can see in my view.

I am almost there, by rotating the image context I get a rotated image:

- (UIImage *) rotatedImageFromImageView: (UIImageView *) imageView
{
    UIImage *rotatedImage;

    // Get image width, height of the bonuding rectangle
    CGRect boundingRect = [self getBoundingRectAfterRotation: imageView.bounds byAngle:angle];

    // Create a graphics context the size of the boundinf rectangle
    UIGraphicsBeginImageContext(boundingRect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

    // Rotate and translate the context
    CGAffineTransform ourTransform = CGAffineTransformIdentity;
    ourTransform = CGAffineTransformConcat(ourTransform, CGAffineTransformMakeRotation(angle));

    CGContextConcatCTM(context, ourTransform);

    // Draw the image into the context
    CGContextDrawImage(context, CGRectMake(0, 0, imageView.image.size.width, imageView.image.size.height), imageView.image.CGImage);

    // Get an image from the context
    rotatedImage = [UIImage imageWithCGImage: CGBitmapContextCreateImage(context)];

    // Clean up
    UIGraphicsEndImageContext();
    return rotatedImage;
 }

However the image is not rotated about its centre. I have tried all kinds of transforms concatenated with my rotate to get it to rotate around the centre but to no avail. Am I missing a trick? Is this even possible since I am rotating the context not the image?

Getting desperate to make this work now, so any help would be appreciated.

Dave

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