iOS image blur effect with category - ios

Question

I'm trying to add a blur effect using category.
+ (UIImage *)blurImageWithImage:(UIImage*) imageName withView:(UIView*)view {
UIImage *sourceImage = imageName;
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"];
// Apply gaussian blur filter with radius of 30
CIFilter *gaussianBlurFilter = [CIFilter filterWithName: #"CIGaussianBlur"];
[gaussianBlurFilter setValue:clampFilter.outputImage forKey: #"inputImage"];
[gaussianBlurFilter setValue:#10 forKey:#"inputRadius"];
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef cgImage = [context createCGImage:gaussianBlurFilter.outputImage fromRect:[inputImage extent]];
// Set up output context.
UIGraphicsBeginImageContext(view.frame.size);
CGContextRef outputContext = UIGraphicsGetCurrentContext();
// Invert image coordinates
CGContextScaleCTM(outputContext, 1.0, -1.0);
CGContextTranslateCTM(outputContext, 0, view.frame.size.height);
// Draw base image.
CGContextDrawImage(outputContext, view.frame, cgImage);
// Apply white tint
CGContextSaveGState(outputContext);
CGContextSetFillColorWithColor(outputContext, [UIColor colorWithWhite:1 alpha:0.2].CGColor);
CGContextFillRect(outputContext, view.frame);
CGContextRestoreGState(outputContext);
// Output image is ready.
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage; }
then I call this function inside a UIView like this:
UIImage *image = [UIImage imageNamed:#"xxx"]
UIImageView *page = [[UIImageView alloc] initWithImage:[UIImage blurImageWithImage:image withView:self]];
If I add this function directly in the class, it works, but not if I do it in UIImage category.

Answer 1

I had face same problem earlier. But thank fully I am getting the solution.
Please follow step. Make sure your blur image function working fine.
1) In category add instance method instead of class method.
ex.
- (UIImage *)blurImageWithImage:(UIImage*) imageName withView:(UIView*)view
2) Import category in your VC
3) Use category, ex
UIImage *image = [UIImage imageNamed:#"xxx"]
UIImageView *page = [[UIImageView alloc] initWithImage:[image blurImageWithImage:image withView:self]];
Let me know this solution is working fine for you.

Answer 2

Turns out the problem was I forgot to add "-" when doing context translate.
So what I ended up doing is I create a class method.
Interface:
+ (UIImage *)blurImageWithImageName:(NSString*) imageName withView:(UIView*)view;
Implementation :
+ (UIImage *)blurImageWithImageName:(NSString*) imageName withView:(UIView*)view {
UIImage *sourceImage = [UIImage imageNamed:imageName];
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"];
// Apply gaussian blur filter with radius of 30
CIFilter *gaussianBlurFilter = [CIFilter filterWithName: #"CIGaussianBlur"];
[gaussianBlurFilter setValue:clampFilter.outputImage forKey: #"inputImage"];
[gaussianBlurFilter setValue:#10 forKey:#"inputRadius"];
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef cgImage = [context createCGImage:gaussianBlurFilter.outputImage fromRect:[inputImage extent]];
// Set up output context.
UIGraphicsBeginImageContext(view.frame.size);
CGContextRef outputContext = UIGraphicsGetCurrentContext();
// Invert image coordinates
CGContextScaleCTM(outputContext, 1.0, -1.0);
CGContextTranslateCTM(outputContext, 0, -view.frame.size.height);
// Draw base image.
CGContextDrawImage(outputContext, view.frame, cgImage);
// Apply white tint
CGContextSaveGState(outputContext);
CGContextSetFillColorWithColor(outputContext, [UIColor colorWithWhite:1 alpha:0.2].CGColor);
CGContextFillRect(outputContext, view.frame);
CGContextRestoreGState(outputContext);
// Output image is ready.
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}