Opencv --- 图像像素遍历的各种方法

#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
using namespace cv;
using namespace std;

// 记录时间信息
void PrintMs(const char *text = "")
{
    static long long last = ;
    long long cur = getTickCount();
    if (last == )
    {
        last = cur;
        return;
    }
    long long ms = ;
    ms = ((double)(cur - last) / getTickFrequency()) * ;
    if (*text != )
    {
        printf("%s = %dms\n", text,ms);
    }
    last = getTickCount();
}
int main(int argc, char *argv[])
{
    Mat mat(, , CV_8UC3);
    //mat.create(3000, 4000, CV_8UC3);
    //元素大小字节数
    int es = mat.elemSize();
    int size = mat.rows*mat.cols*es;

    //地址遍历连续的Mat
    PrintMs();
    for (int i = ; i < size; i += es)
    {
        mat.data[i] = ;    //B
        mat.data[i + ] = ;//G
        mat.data[i + ] = ;//R
    }
    PrintMs("mat.data ms");

    //地址遍历不一定连续的Mat
    for (int row = ; row < mat.rows; row++)
    {
        for (int col = ; col < mat.cols; col++)
        {
            (&mat.data[row*mat.step])[col*es] = ;//B
            (&mat.data[row*mat.step])[col*es+] = ;//G
            (&mat.data[row*mat.step])[col*es+] = ;//R
        }
    }
    PrintMs("mat.step ms");

    //使用ptr遍历Mat
    for (int row = ; row < mat.rows; row++)
    {
        for (int col = ; col < mat.cols; col++)
        {
            Vec3b *c = mat.ptr<Vec3b>(row, col);
            c->val[] = ;        //B
            c->val[] = ;    //G
            c->val[] = ;        //R
        }
    }
    PrintMs("mat.ptr ");
    try
    {
        //使用at来遍历
        for (int row = ; row < mat.rows; row++)
        {
            for (int col = ; col < mat.cols; col++)
            {
                Vec3b &m = mat.at<Vec3b>(row, col);
                m[] = ;
                m[] = ;
                m[] = ;
            }
        }
        PrintMs("mat.at");
    }
    catch (Exception &ex)
    {
        cout << ex.what() << endl;
    }

    //通过迭代器来遍历
    PrintMs("");
    auto it = mat.begin<Vec3b>();
    auto it_end = mat.end<Vec3b>();
    for (; it != it_end; it++)
    {
        (*it).val[] = ;    //B
        (*it).val[] = ;    //G
        (*it).val[] = ;    //R
    }
    PrintMs("mat.itr");

    namedWindow("mat");
    imshow("mat", mat);
    waitKey();

    return ;
}