How to increase the Gaussian Blur as the user scrolls up - ios

Question

I have a UIImage inside UIImageView on which gaussian blur filter with radius of 50 has been applied as of now. As per the new requirement, I need to set its initial Gaussian Blur at 3px. Then increase it slowly from 3px to 10 px as the user scrolls up the view? Could anybody please help me understand how can this be done?
This is the code that I'm using to blur the image as of now with a radius of 50.
- (UIImage *)blurWithCoreImage:(UIImage *)sourceImage blurValue:(int)valBlur
{
CIImage *inputImage = [CIImage imageWithCGImage:sourceImage.CGImage];
// Apply Affine-Clamp filter to stretch the image so that it does not
// look shrunken when gaussian blur is applied
CGAffineTransform transform = CGAffineTransformIdentity;
CIFilter *clampFilter = [CIFilter filterWithName:#"CIAffineClamp"];
[clampFilter setValue:inputImage forKey:#"inputImage"];
[clampFilter setValue:[NSValue valueWithBytes:&transform objCType:#encode(CGAffineTransform)] forKey:#"inputTransform"];
CIFilter *gaussianBlurFilter = [CIFilter filterWithName: #"CIGaussianBlur"];
[gaussianBlurFilter setValue:clampFilter.outputImage forKey: #"inputImage"];
[gaussianBlurFilter setValue:[NSString stringWithFormat:#"%d",valBlur] forKey:#"inputRadius"];
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef cgImage = [context createCGImage:gaussianBlurFilter.outputImage fromRect:[inputImage extent]];
// Set up output context.
UIGraphicsBeginImageContext(self.view.frame.size);
CGContextRef outputContext = UIGraphicsGetCurrentContext();
// Invert image coordinates
CGContextScaleCTM(outputContext, 1.0, -1.0);
CGContextTranslateCTM(outputContext, 0, -self.view.frame.size.height);
// Draw base image.
CGContextDrawImage(outputContext, self.view.frame, cgImage);
// Apply white tint
CGContextSaveGState(outputContext);
CGContextSetFillColorWithColor(outputContext, [UIColor colorWithWhite:1 alpha:0.2].CGColor);
CGContextFillRect(outputContext, self.view.frame);
CGContextRestoreGState(outputContext);
// Output image is ready.
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}

Answer 1

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
/* This is the offset at the bottom of the scroll view. */
CGFloat totalScroll = scrollView.contentSize.height - scrollView.bounds.size.height;
/* This is the current offset. */
CGFloat offset = - scrollView.contentOffset.y;
/* This is the percentage of the current offset / bottom offset. */
CGFloat percentage = offset / totalScroll;
/* When percentage = 0, the Blur should be 3 so we should flip the percentage. */
imageview.blurLevel= (3.0f + percentage);
}
Source : SFOS