OpenCV使用forEach的方式来遍历像素值

opencv 4.x新增了forEach的方式遍历像素值，比传统方式略快一些。因为它本身是使用多线程并行的方法来遍历的。从opencv源码能看到这句话：

parallel_for_(cv::Range(0, LINES), PixelOperationWrapper(reinterpret_cast(this), operation));

写了一个测试用例，把它用起来。包括单通道，三通道，浮点型等cv::Mat的遍历。

#include 
typedef cv::Point3_ Pixel;
void test1(cv::Mat &image)
{
    //raw pointer access.
    double start = (double)cv::getTickCount();
    for (int r = 0; r x = 255 - ptr->x;
            ptr->y = 255 - ptr->y;
            ptr->z = 255 - ptr->z;
        }
    }
    double time = (((double)cv::getTickCount() - start)) / cv::getTickFrequency();
    printf(" raw pointer access time1 : %.4f seconds\n", time);
}
void test2(cv::Mat &image)
{
    double start = (double)cv::getTickCount();
    int w = image.cols;
    int h = image.rows;
    for (int row = 0; row  void {
        p.x = 255 - p.x;
        p.y = 255 - p.y;
        p.z = 255 - p.z;
    });
    double time = (((double)cv::getTickCount() - start)) / cv::getTickFrequency();
    printf(" forEach time3 : %.4f seconds\n", time);
}
void test4(cv::Mat &image)
{
    cv::Mat gray;
    cv::cvtColor(image, gray, cv::COLOR_BGR2GRAY);
    //遍历单通道图像
    //position是遍历的像素点坐标位置
    //position[0]=row, position[1]=col
    gray.forEach([](uint8_t &p, const int *position) -> void {
        p += 1;
    });
}
void test5(cv::Mat &image)
{
    cv::Mat gray;
    cv::cvtColor(image, gray, cv::COLOR_BGR2GRAY);
    cv::Mat ft;
    gray.convertTo(ft, CV_32FC1, 1.0 / 255.0);
    //多线程并行遍历像素,需要加锁
    float score = 0.8;
    std::vector vtPos;
    std::vector vtConfidences;
    std::mutex mtx;
    ft.forEach([&vtConfidences, &vtPos, &score, &mtx](float &val, const int *position) -> void {
        if (val > score)
        {
            mtx.lock();
            vtPos.emplace_back(cv::Point(position[1], position[0])); //x,y==col,row
            vtConfidences.emplace_back(val);
            mtx.unlock();
        }
    });
    std::cout