title: Linker error using CIFilter
body: <p>I'm getting the following linker errors when I try to use CIFilter in iOS 5. </p>
  
  <pre><code>Undefined symbols for architecture i386: "_OBJC_CLASS_$_CIFilter", referenced from: objc class-ref in libios_ngn_stack.a(NgnProxyVideoConsumer.o)"_kCIInputImageKey", referenced from:
  </code></pre>
  
  <p>The line that causes the error is:</p>
  
  <pre><code>CIFilter *filter = [CIFilter filterWithName:@"CISepiaTone" 
                                            keysAndValues: kCIInputImageKey, image, 
                                  @"inputIntensity", [NSNumber numberWithFloat:0.8], nil];
  </code></pre>
  
  <p>Somebody had the same issue in <a href="https://stackoverflow.com/questions/7969797/how-do-i-resolve-the-linker-error-when-i-try-to-use-cifilter-in-my-ios-iphone">this question</a>, but the only answer was that he need sLibrary/Frameworks/CoreImage.framework. Could somebody elaborate on how I would go about installing this ramework? (I do have a CoreImage framework in Library/Frameworks/QuartzCore/Frameworks/CoreImage...)</p>
  
  <p>Any help would be appreciated</p>