​​​​​​OpenCV Basic introduction series basic operation —— one _ Zero one game blog -CSDN Blog c

Refer to this blog

OpenCV course — OpenCV 2.3.2 documentation

This tutorial is very good

One . Gray processing image

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
#define rep(i, a, b) for(int i = (a); i < (b); i++)
using namespace cv;
using namespace std;

int main()
{
    Mat img = imread("1.jpg");
    int n = img.rows;
    int m = img.cols;
    
    rep(i, 0, n)
        rep(j, 0, m)
        {
            uchar averge = (img.at<Vec3b>(i, j)[0] + img.at<Vec3b>(i, j)[1] + img.at<Vec3b>(i, j)[2]) / 3;
            rep(k, 0, 3) img.at<Vec3b>(i, j)[k] = averge;
        }

    imshow("picture", img);
    waitKey(0);

    return 0;
}

Two . Binary operation

Just change the value a little

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
#define rep(i, a, b) for(int i = (a); i < (b); i++)
using namespace cv;
using namespace std;

int main()
{
    Mat img = imread("1.jpg");
    int n = img.rows;
    int m = img.cols;
    
    rep(i, 0, n)
        rep(j, 0, m)
        {
            uchar averge = (img.at<Vec3b>(i, j)[0] + img.at<Vec3b>(i, j)[1] + img.at<Vec3b>(i, j)[2]) / 3;
            if (averge > 150) averge = 255;
            else averge = 0;
            rep(k, 0, 3) img.at<Vec3b>(i, j)[k] = averge;
        }

    imshow("picture", img);
    waitKey(0);

    return 0;
}

3、 ... and . The channel separation

Be careful opencv Medium is BGR

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
#define rep(i, a, b) for(int i = (a); i < (b); i++)
using namespace cv;
using namespace std;

int main()
{
	Mat image = imread("1.jpg");

	vector<Mat> channels;
	split(image, channels);
	imshow("B", channels.at(0));
	imshow("G", channels.at(1));
	imshow("R", channels.at(2));
	waitKey(0);

    return 0;
}

Four .cvtColor Use of functions

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
#define rep(i, a, b) for(int i = (a); i < (b); i++)
using namespace cv;
using namespace std;

int main()
{
	Mat img = imread("1.jpg"), img2, img3;

	cvtColor(img, img2, CV_BGR2GRAY);
	cvtColor(img, img3, COLOR_BGR2Lab);
	imshow("picture1", img);
	imshow("picture2", img2);
	imshow("picture3", img3);
	waitKey(0);

    return 0;
}

5、 ... and .namedwindow Use of functions

The second parameter is 0 Indicates that the window can be resized ,1 Means impossible

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
#define rep(i, a, b) for(int i = (a); i < (b); i++)
using namespace cv;
using namespace std;

int main()
{
	Mat img = imread("1.jpg");
	namedWindow("1", 0);
	//namedWindow("1", 1);
	imshow("1", img);

	waitKey(0);

    return 0;
}

6、 ... and . wave filtering

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
using namespace cv;
using namespace std;

int main()
{
	Mat img = imread("1.jpg");

	imshow("1", img);
	blur(img, img, Size(5, 5));     // Mean filtering   Fuzzy 
	//medianBlur(img, img, 5);      // median filtering   Eliminate noise 
	imshow("2", img);
	waitKey(0);

    return 0;
}

7、 ... and . Histogram equalization

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
using namespace cv;
using namespace std;

int main()
{
	Mat img = imread("1.jpg"), img2;
	cvtColor(img, img, CV_BGR2GRAY);
	equalizeHist(img, img2);

	imshow("1", img);
	imshow("2", img2);
	waitKey(0);

    return 0;
}

Realize it by yourself

#include <opencv2/opencv.hpp>
#include <cmath>
using namespace cv;

const int N = 260;
int cnt[N], map[N];

int main()
{
	Mat img = imread("2.jpg");
	cvtColor(img, img, CV_BGR2GRAY);
	imshow(" Before processing ", img);

	int n = img.rows, m = img.cols;
	for (int i = 0; i < n; i++)
		for (int j = 0; j < m; j++)
			cnt[img.at<uchar>(i, j)]++;

	int sum = 0;
	for (int i = 0; i < 256; i++)
	{
		sum += cnt[i];
		map[i] = round(255.0 * sum / (m * n));
	}

	for (int i = 0; i < n; i++)
		for (int j = 0; j < m; j++)
			img.at<uchar>(i, j) = map[img.at<uchar>(i, j)];

	imshow(" After processing ", img);
	waitKey(0);

	return 0;
}

8、 ... and . edge detection drawing

#include <opencv2/opencv.hpp>
using namespace cv;

int main()
{
    Mat img, img2, img3;
    img = imread("3.jpg");
    imshow("input", img);

    /*  Draw a straight line 
    line(img, Point(1, 1), Point(50, 50), Scalar(0, 0, 255), 2);
    imshow("output", img);
    */

    /* Sobel Operator implementation of edge detection 
    cvtColor(img, img, CV_RGB2GRAY);
    Sobel(img, img2, -1, 1, 0);        // -1 Represents the image depth   All written -1 That's it    1 0  Express x Direction  0 1  Express y Direction 
    Sobel(img, img3, -1, 0, 1);        
    namedWindow("output2", 0);           
    namedWindow("output3", 0);
    imshow("output2", img2);
    imshow("output3", img3);*/

    waitKey(0);

    return 0;
}

Nine . Profile analysis Find and draw

OpenCV Medium findContours Function parameter details _ The small white _ Strive -CSDN Blog _findcontours

Ten .Hough Transform detection line

#include <opencv2/opencv.hpp>
#include <bits/stdc++.h>
using namespace cv;
using namespace std;

int main()
{
    Mat img, t;
    img = imread("1.jpg");
   // imshow("input", img);

    // use Canny Two valued 
    cvtColor(img, t, CV_RGB2GRAY);            // First convert to grayscale 
    GaussianBlur(t, t, Size(3, 3), 0, 0);   // Gaussian filter is used to remove noise 
    Canny(t, t, 125, 350);                  // use Canny edge detection 

    //ROI  Select the area of interest 
    imshow("output1", t);
    for (int i = 0; i < t.rows; i++)
        for (int j = 0; j < t.cols; j++)
               if(j < 700 || j > 1200)
                    t.at<uchar>(i, j) = 0;
    imshow("output2", t);

    // use Hough Transform detection line 
    vector<Vec4i> lines;                        //lines Each element in stores a quadruple   Two points and four coordinates representing a straight line 
    HoughLinesP(t, lines, 1, CV_PI / 180, 80, 100, 50);
    for (auto x : lines)
    {
        if (x[0] == x[2]) continue;
        double k = double(x[3] - x[1]) / (x[0] - x[2]);
        if (k > 0 || abs(k) < 2 || abs(k) > 10) continue;     // Limit the slope of the line 
        line(img, Point(x[0], x[1]), Point(x[2], x[3]), Scalar(0, 255, 0), 10);
    }
        
    namedWindow("output", 0);
    imshow("output", img);
    waitKey(0);

    return 0;
}

11、 ... and . Video reading and writing

#include<opencv2/opencv.hpp>
using namespace cv;

int main()
{
    VideoCapture vc;
    vc.open("1.avi");
    if (!vc.isOpened())
    {
        printf("can not open ...\n");
        return -1;
    }

    VideoWriter vw;
    vw.open("output.avi", (int)vc.get(CV_CAP_PROP_FOURCC), (double)vc.get(CV_CAP_PROP_FPS),
    Size((int)vc.get(CV_CAP_PROP_FRAME_WIDTH), (int)vc.get(CV_CAP_PROP_FRAME_HEIGHT)), true);

    Mat frame;
    while (vc.read(frame))
    {
        // This line can handle the current frame , That is to say frame This image 
        vw.write(frame);
    }
    vc.release();
    vw.release();

    return 0;
}

Twelve . Lane line detection

#include<opencv2/opencv.hpp>
#include<bits/stdc++.h>
using namespace cv;
using namespace std;

int fi = 1, d, last;

void draw(Mat& img, int x)
{
    circle(img, Point(last = x, img.rows - 10), 10, Scalar(0, 0, 255), -1);
}

void deal(Mat& img)
{
    Mat t;

    // use Canny Two valued 
    cvtColor(img, t, CV_RGB2GRAY);            // First convert to grayscale 
    GaussianBlur(t, t, Size(3, 3), 0, 0);   // Gaussian filter is used to remove noise 
    Canny(t, t, 125, 350);                  // use Canny edge detection 

    // use Hough Transform detection line 
    vector<Vec4i> lines;                        //lines Each element in stores a quadruple   Two points and four coordinates representing a straight line 
    vector<int> node;                           // Save the intersection of the straight line and the baseline 
    HoughLinesP(t, lines, 1, CV_PI / 180, 80, 100, 50); // The last two parameters correspond to minLineLength  maxLineGap
    for (auto x : lines)
    {
        int x1 = x[0], y1 = x[1], x2 = x[2], y2 = x[3];
        if (x1 == x2) continue;
        double k = double(y1 - y2) / (x1 - x2);
        if (k > 0 && 2 <= abs(k) && abs(k) <= 10)// Limit the slope of the line      
        {
            //  line(img, Point(x1, y1), Point(x2, y2), Scalar(0, 255, 0), 5);
            int xx = (img.rows - y1) / k + x1;
            node.push_back(xx);
        }
    }

    // Intersection de duplication 
    vector<int> ve;
    sort(node.begin(), node.end());
    for (int i = 0; i < node.size(); i++)
    {
        if (i + 1 < node.size() && node[i + 1] - node[i] <= 10)
        {
            node[i + 1] = node[i];
            continue;
        }
        ve.push_back(node[i]);
    }

    // Draw red dots 
    if (fi)    // First frame 
    {
        d = ve[1] - ve[0];
        draw(img, ve[0] + d);
        fi = 0;
    }
    else
    {
        if (!ve.size()) draw(img, last);                             // The left and right straight lines are not detected 
        else
        {
            if (abs(ve[0] + d - last) <= 30) draw(img, ve[0] + d);   // The left straight line is detected 
            else draw(img, ve[0]);                                   // The left straight line is not detected 
        }
    }
}

int main()
{
    VideoCapture vc;
    vc.open("03.avi");
    if (!vc.isOpened())
    {
        printf("can not open ...\n");
        return -1;
    }

    VideoWriter vw;
    vw.open("output3.avi", (int)vc.get(CV_CAP_PROP_FOURCC), (double)vc.get(CV_CAP_PROP_FPS),
        Size((int)vc.get(CV_CAP_PROP_FRAME_WIDTH), (int)vc.get(CV_CAP_PROP_FRAME_HEIGHT)), true);

    Mat frame;
    while (vc.read(frame))
    {
        deal(frame);
        vw.write(frame);
    }
    vc.release();
    vw.release();

    return 0;
}