I see the same leak you're seeing when profiling the code. Try this instead which seems to avoid the leak and give you the same results:
- (UIImage*)blurImage:(UIImage*)image withStrength:(float)strength
{
@autoreleasepool {
CIImage* inputImage = [[CIImage alloc] initWithCGImage:image.CGImage];
CIFilter* filter = [CIFilter filterWithName:@"CIGaussianBlur"];
[filter setValue:inputImage forKey:@"inputImage"];
[filter setValue:[NSNumber numberWithFloat:strength] forKey:@"inputRadius"];
CIImage* result = [filter valueForKey:kCIOutputImageKey];
float scale = [[UIScreen mainScreen] scale];
CIImage* cropped = [result imageByCroppingToRect:CGRectMake(0, 0, image.size.width * scale, image.size.height * scale)];
return [[UIImage alloc] initWithCIImage:cropped];
}
}