Fast blur on iOS

Question

I\'m running into trouble trying to blur part of the screen in my iOS app. See image for better idea of what I\'m trying to do.

Answer 1

I would recommend Brad Larson's GPUImage which is fully backed by the GPU for a wide variety of image processing effects. It's very fast, and even fast enough that in his demo app he does real-time video processing from the camera and the frame-rate is excellent.

https://github.com/BradLarson/GPUImage

Here is a code snippet I wrote to apply a basic box blur which blurs the bottom and top thirds of the image but leaves the middle of the image un-blurred. His library is extremely extensive and contains almost every kind of image filter effect imaginable.

GPUImagePicture *stillImageSource = [[GPUImagePicture alloc] initWithImage:[self screenshot]];

GPUImageTiltShiftFilter *boxBlur = [[GPUImageTiltShiftFilter alloc] init];
        boxBlur.blurSize = 0.5;

[stillImageSource addTarget:boxBlur];

[stillImageSource processImage];

UIImage *processedImage = [stillImageSource imageFromCurrentlyProcessedOutput];