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Applying CIFilter on Image in an UIImageView

February 1, 2012

In my latest App Filterastic+ I’m using CIFilter which was introduced in iOS 5. CIFilter class allows you to apply a filter to an CIImage. I will show you how you can use CIFilter with an UIImage object and in extend with an UIImageView.

//imgView is the UIImageView I’m using to display an UIImage to the user

//Put it all into an NSAutoreleasePool and release it when you are done or else the memory allocated by CIContext will increase every time you apply a filter
NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];

//First of all keep a copy of the original image orientation
//you’ll need it afterwards
UIImageOrientation originalOrientation = self.imgView.image.imageOrientation;

//Then you need to create the CIImage from the UIImage
//I used the CGImage property of the UIImage class and created the CIImage from the CGImage
CIImage *inputImage = [[CIImage alloc] initWithCGImage:[self.imgView.image CGImage]];

//Then create the CIFilter you want
//I’m using sepia in this example
CIFilter adjustmentFilter = [CIFilter filterWithName:@”CISepiaTone”];
[adjustmentFilter setDefaults];
[adjustmentFilter setValue:inputImage forKey:@”inputImage”];
[adjustmentFilter setValue:[NSNumber numberWithFloat:1.0f] forKey:@”inputIntensity”];

// The output CIImage with the sepia effect applied
CIImage *outputImage = [adjustmentFilter valueForKey:@”outputImage”];

//Create a CIContext
CIContext* context = [CIContext contextWithOptions:nil];

//Create an CGImageRef from the output CIImage
CGImageRef imgRef = [context createCGImage:outputImage fromRect:outputImage.extent] ;

// Create an UIImage from the CGImageRef object with scale = 1.0 and the orientation of the original image
UIImage* img = [[UIImage alloc] initWithCGImage:imgRef scale:1.0 orientation:originalOrientation];

//Release the CGImageRef object

//set the UIImage object to the UIImageView
self.imgView.image = img;

// release stuff
[img release];
[inputImage release];
[pool release];

From → Code Snippets

  1. Navn permalink

    Good one… But its not working with CILineOverlay CIFilter… Can u plz help me.. Thanks in advance…

  2. @Navn CILineOverlay isn’t supported in iOS yet, it’s only available on Mac OS X.

  3. Ahkhan permalink

    OMG! I have been stuck in this problem for over a week. Thank you!

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