RT，支持iOS 6.0 and later

    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"1.png"]];
    // create gaussian blur filter
    CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [filter setValue:inputImage forKey:kCIInputImageKey];
    [filter setValue:[NSNumber numberWithFloat:10.0] forKey:@"inputRadius"];
    // blur image
    CIImage *result = [filter valueForKey:kCIOutputImageKey];
    CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];
    UIImage *image = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);
    self.mainImageView.image = image;

效果如下：