UIImage Blur Category

gistfile1.m

#import <CoreImage/CoreImage.h>
 
@implementation UIImage (Blur)
 
+(UIImage *)darkenedAndBlurredImageForImage:(UIImage *)image {
    CGFloat scaleFactor = 1.0f;
 
    if (AppDelegate.device == TLAppDelegateDeviceIPhone3GS || AppDelegate.device == TLAppDelegateDeviceIPhone4) {
        scaleFactor = 0.25f;
    } else if (AppDelegate.device == TLAppDelegateDeviceIPhone4S) {
        scaleFactor = 0.5f;
    }
 
    CIImage *inputImage = [[[CIImage alloc] initWithImage:image] imageByApplyingTransform:CGAffineTransformMakeScale(scaleFactor, 0.25f)];
 
    CIContext *context = [CIContext contextWithOptions:nil];
 
    //First, create some darkness
    CIFilter *blackGenerator = [CIFilter filterWithName:@"CIConstantColorGenerator"];
    CIColor *black = [CIColor colorWithString:@"0.0 0.0 0.0 0.92"];
    [blackGenerator setValue:black forKey:@"inputColor"];
    CIImage *blackImage = [blackGenerator valueForKey:@"outputImage"];
 
    //Second, apply that black
    CIFilter *compositeFilter = [CIFilter filterWithName:@"CISourceOverCompositing"];
    [compositeFilter setValue:blackImage forKey:@"inputImage"];
    [compositeFilter setValue:inputImage forKey:@"inputBackgroundImage"];
    CIImage *darkenedImage = [compositeFilter outputImage];
 
    //Third, blur the image
    CIFilter *blurFilter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [blurFilter setDefaults];
    [blurFilter setValue:@(2 * scaleFactor) forKey:@"inputRadius"];
    [blurFilter setValue:darkenedImage forKey:kCIInputImageKey];
    CIImage *blurredImage = [blurFilter outputImage];
 
    CGImageRef cgimg = [context createCGImage:blurredImage fromRect:inputImage.extent];
    UIImage *blurredAndDarkenedImage = [UIImage imageWithCGImage:cgimg];
    CGImageRelease(cgimg);
 
    return blurredAndDarkenedImage;
}
 
@end