title: CIBloom makes image smaller
body: <p>I'm using CIBloom to blur some text inside a <code>CGImage</code>, but what is happening is the CIBloom filter seems to be <strong><em>making my image very slightly smaller</em></strong>.</p>
  
  <p>The effect is worse when the filter kernel is made bigger.  I kind of expected this but I need a way to turn it off, or a formula to resize the image so that each letter is exactly the same size that it originally was.  I'm leaving margins on my source image on purpose.</p>
  
  <p>Before CIBloom filter:</p>
  
  <p><img src="https://i.stack.imgur.com/fYuaX.png" alt="a"></p>
  
  <p>After CIBloom filter:</p>
  
  <p><img src="https://i.stack.imgur.com/o0BI4.png" alt="enter image description here"></p>
  
  <p>The code that blurs the filter:</p>
  
  <pre><code>CGImageRef cgImageRef = CGBitmapContextCreateImage( tex-&gt;cgContext ) ;
  
  CIImage *cii = [CIImage imageWithCGImage:cgImageRef] ;
  
  CIFilter *filter = [CIFilter filterWithName:@"CIBloom"] ; //CIGaussianBlur
  
  [filter setValue:cii forKey:kCIInputImageKey];
  [filter setValue:[NSNumber numberWithFloat:1.1f] forKey:@"inputIntensity"];
  
  // Large radius makes result EVEN SMALLER:
  //[filter setValue:[NSNumber numberWithFloat:100.f] forKey:@"inputRadius"];
  
  CIContext *ciContext = [CIContext contextWithOptions:nil];
  
  CIImage *ciResult = [filter valueForKey:kCIOutputImageKey];
  CGImageRef cgIRes = [ciContext createCGImage:ciResult fromRect:[ciResult extent]];
  
  //Clear old tex
  tex-&gt;clearBacking( 0, 0, 0, 1 ) ;
  
  // Drop CIImage result into texture raw data
  CGContextDrawImage( tex-&gt;cgContext, CGRectMake(0, 0, tex-&gt;w, tex-&gt;h), cgIRes ) ;
  </code></pre>
  
  <p>I like the <code>CIBloom</code> filter, but I need the results to be <strong>the same size as my original image</strong>, not downsampled.</p>