GPUImage需要很长时间才能在iphone4 4s中保存图像。我能怎么做？

Question

我在视图类中定义了这个函数， filter = GPUImageWhiteBalanceFilter

[self.stillCamera capturePhotoAsImageProcessedUpToFilter:self.filter withCompletionHandler:^(UIImage * image,NSError * error){
        @autoreleasepool {
            if (!image) {//得到照片发生错误
                if ([self.delegate respondsToSelector:@selector(gpuImageCameraViewStillImageCaptured:image:error:)]) {
                    [self.delegate gpuImageCameraViewStillImageCaptured:self image:nil error:error];
                }
            }
            else{
                if ([self.delegate respondsToSelector:@selector(gpuImageCameraViewStillImageCaptured:image:error:)]) {
                    [self.delegate gpuImageCameraViewStillImageCaptured:self image:image error:nil];
                }
            }
        }
    }];

我在ViewController中像这样完成委托

NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(savePhotosThreadSingle:) object:image];
    [_threadQueue addOperation:op];
    [op release];

savePhotosThreadSingle：是一种将图像保存到照片库的方法 但在iPhone4s中需要大约3秒才能保存此图像我该怎么办？谢谢