opencv:访问像素

a.使用指针

#include <opencv.hpp>
using namespace cv;
using namespace std;
int main()
{
    //指针访问每个像素并赋值
    Mat img = imread("001.jpg");
    for (int i = 0; i < img.rows; i++)
    {
        uchar* data = img.ptr<uchar>(i); // 获取每i行的首地址
        for (int j = 0; j < (img.cols*img.channels())/*列数乘以通道数*/; j++)
            data[j] = 200;
    }
    imshow("2", img);
    waitKey(0);
    
    return 0;
}

b.通过迭代器

#include <opencv.hpp>
using namespace cv;
using namespace std;
int main()
{
    //使用迭代器
    Mat img = imread("001.jpg");
    Mat_<Vec3b>::iterator it = img.begin<Vec3b>(); // 迭代器的初始位置
    Mat_<Vec3b>::iterator itend = img.end<Vec3b>(); // 迭代器的终止位置
    for (; it != itend; it++)
    {
        (*it)[0] = 0;
        (*it)[2] = 0;
        (*it)[1] = 255;
    }
    imshow("2", img);
    waitKey(0);
    
    return 0;
}

c.通过地址计算

#include <opencv.hpp>
using namespace cv;
using namespace std;
int main()
{
    //动态地址计算 use .at
    Mat img = imread("001.jpg");
    for (int i = 0; i < img.rows; i++)
    for (int j = 0; j < img.cols; j++)
    {
        img.at<Vec3b>(i, j)[0] = 0;
        img.at<Vec3b>(i, j)[1] = 0;
        img.at<Vec3b>(i, j)[2] = 244;
    }
    imshow("2", img);
    waitKey(0);
    
    return 0;
}