title: Using CINoiseReduction - get blank image?
body: <p>I am playing around with CI filters, but am having a spot of trouble with de-noising. Basically I get a blank image from this. </p>
  
  <p>I am sure that I am just missing something simple.</p>
  
  <p>Here's my code:</p>
  
  <pre><code>CGImageRef imageRef = [self.iv.image CGImage];
  CIContext *context = [CIContext contextWithOptions:nil]; // 1
  CIImage *ciImage = [CIImage imageWithCGImage:imageRef]; // 2
  CIFilter *filter = [CIFilter filterWithName:@"CINoiseReduction" ];
  [filter setDefaults];
  [filter setValue:ciImage forKey:@"inputImage"]; // 3
  CIImage *ciResult = [filter valueForKey:kCIOutputImageKey]; // 4
  CGImageRef cgImage = [context createCGImage:ciResult fromRect:[ciResult extent]];
  UIImage *img = [UIImage imageWithCGImage:cgImage];
  self.iv.image = img;
  </code></pre>