Rotate UIImage without quality loss

Question

I have a problem to rotate UIImage without quality loss. Now I am using ready method provided by BFKit imageRotatedByDegrees:, but my image become diffused (blurred).

Sample code:

UIImage *image = [[UIImage imageNamed:@"car"] imageRotatedByDegrees:(((float)arc4random() / ARC4RANDOM_MAX) * (360))];

Code of imageRotatedByDegrees: :

- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees 
{   
    // calculate the size of the rotated view's containing box for our drawing space
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
    CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;

    // Create the bitmap context
    UIGraphicsBeginImageContext(rotatedSize);
    CGContextRef bitmap = UIGraphicsGetCurrentContext();

    // Move the origin to the middle of the image so we will rotate and scale around the center.
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

    //   // Rotate the image context
    CGContextRotateCTM(bitmap, DegreesToRadians(degrees));

    // Now, draw the rotated/scaled image into the context
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

Is there another way to rotate UIImage without quality loss?

Answer 1

I'm the author of BFKit, and when I read about your question I investigated about that issue. In the latest version (1.6.4) I've fixed that!

Now the image will no more be diffused (blurred).

Answer 2

My aim was to rotate an image that was in my MKAnnotationView. So I solved the problem by rotating not image, but whole MKAnnotationView.

An answer which helped me is this.

My code in MKMapViewDelegate method mapView:viewForAnnotation::

annotationView.transform = CGAffineTransformMakeRotation((((float)arc4random() / ARC4RANDOM_MAX) * (360)));