Hegong sky team vision training Day2 - traditional vision, opencv basic operation

Catalog

Learning goals

Learning content

Learning time

Learning output

One 、 Thinking questions

1、OpenCV Library and Matlab、halcon The difference between ？

2、 After display , No use destroyWindow() What's the difference? ？

3、png Picture format and jpg What is the difference between picture formats ？

Two 、 Exercises （C++ Realization ）

1. Display two pictures with different resolutions at the same time , Compare their size

2. Use Opencv, Test the resolution and frame rate of your computer camera

3. Take an image of yourself from the outside with a computer camera , Add circle （ Or other graphics ） Code yourself , At the same time, you can change the resolution by pressing the key , And add time in the lower right corner of the picture

3、 ... and 、 Exercises （python Realization ）

1. Display two pictures with different resolutions at the same time , Compare their size

2. Use Opencv, Test the resolution and frame rate of your computer camera

3. Take an image of yourself from the outside with a computer camera , Add circle （ Or other graphics ） Code yourself , At the same time, you can change the resolution by pressing the key , And add time in the lower right corner of the picture

The learning

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Learning goals

• understand Opencv The development history 、Opencv Version difference

• Master the reading of pictures and videos 、 Show 、 Save method

• master Opencv Basic drawing operations

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Learning content

1. build opencv development environment
2. master opencv Simple operation

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Learning time

• 2022 year 7 month 19 Japan

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Learning output

The following is the overall learning process （ The code to build , Question answering process ）, In terms of code implementation, I start from C++ Language and python Language starts from two directions , On the whole, the former is more difficult to achieve than the latter .

Please refer to , It's very detailed ：vs2022 stay win11 The configuration opencvhttps://blog.csdn.net/Burp_Boom/article/details/124163830?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165823862616782246495908%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=165823862616782246495908&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~first_rank_ecpm_v1~rank_v31_ecpm-9-124163830-null-null.142^v32^pc_search_v2,185^v2^control&utm_term=opencv%E5%AE%89%E8%A3%85%E6%95%99%E7%A8%8Bvs2022&spm=1018.2226.3001.4187

One 、 Thinking questions

1、OpenCV Library and Matlab、halcon The difference between ？

Halcon And OpenCV All belong to the function library , All provide interfaces accessed by multiple programming languages , and Matlab It is a complete integrated development environment , Including the editor 、 function library 、 also Matlab Language . For example, use Matlab Can directly Debug, But with Halcon and OpenCV Relevant code development needs cooperation IDE.Opencv： They are good at recognition , For example, face recognition 、 Video recognition, etc ;Halcon： In dimension measurement , Feeling Halcon Well done , Its calibration package is better , Measurement can directly come out the size , It's more convenient .
 

2、 After display , No use destroyWindow() What's the difference? ？

destroyWindow() Used to close a specific window , Fill in the name of the window in brackets , The type is string.
 

3、png Picture format and jpg What is the difference between picture formats ？

1.jpg It belongs to a lossy compressed picture file , It is a popular image file format in the network ,jpg The image file can be compressed to the smallest format ;png It belongs to lossless compressed picture file ,PNG-8 Support transparency , However, translucency is not supported , therefore PS When storing, there will be miscellaneous edge colors .PNG-24 Support transparency , Support translucency , The size of the stored file will be larger than PNG-8 Big .

2.jpg Format pictures can be highly compressed at the same time , It can show very vivid and rich images , But with the increase of compression , The picture quality will gradually decline ; however png The picture is different , Small volume , Less space , And jpg Compared with the format ,png Pictures without losing picture data , You can get the pictures you need more quickly , And the quality of the picture will not decline .
3.png Format pictures can be edited , For example, the text style in the picture , Lines, etc , It can be used ps Software changes such as ;jpg The picture in format cannot be edited normally .png And jpg Picture comparison png The format of the picture is larger .

Two 、 Exercises （C++ Realization ）

1. Display two pictures with different resolutions at the same time , Compare their size

Very regret ,OpenCV There doesn't seem to be anything like that in China Matlab Similar functions in , So we need to customize the function , The core idea is to display the image as needed , Create a new big image , Use ROI Operate to copy the image to be displayed into the new large image .
 

#include <opencv2\opencv.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;

Mat combineImages(vector<Mat> imgs,int col,int row,bool hasMargin);// Function declaration 

int main(){
    vector<Mat> imgs(2);
    imgs[0] = imread("D:/xxxxxx");
    imgs[1] = imread("D:/xxxxxx");

    Mat m = combineImages(imgs, 2, 2, false);
    namedWindow("test",0);
    imshow("test", m);
    //imwrite("D:/research/Test1/rawimage/0.jpg", m);
    waitKey(0);
    return 0;
}

Mat combineImages(vector<Mat> imgs,
                  int col,
                  int row, 
                  bool hasMargin){
    int imgAmount = imgs.size();
    int width = imgs[0].cols;
    int height = imgs[0].rows;
    int newWidth, newHeight;
    if (！hasMargin){
        newWidth = col*imgs[0].cols;
        newHeight = row*imgs[0].rows;
    }
    else{
        newWidth = (col + 1) * 20 + col*width;
        newHeight = (row + 1) * 20 + row*height;
    }

    Mat newImage(newHeight, newWidth, CV_8UC3, Scalar(255, 255, 255));


    int x, y,imgCount;
    if (hasMargin){
        imgCount = 0;
        x = 0; y = 0;
        while (imgCount < imgAmount){
            Mat imageROI = newImage(Rect(x*width + (x + 1) * 20, y*height + (y + 1) * 20, width, height));// Create regions of interest 
            imgs[imgCount].copyTo(imageROI);
            imgCount++;
            if (x == (col - 1)){
                x = 0;
                y++;
            }
            else{
                x++;
            }
        }
    }
    else{
        imgCount = 0;
        x = 0; y = 0;
        while (imgCount < imgAmount){
            Mat imageROI = newImage(Rect(x*width, y*height, width, height));
            imgs[imgCount].copyTo(imageROI);
            imgCount++;
            if (x == (col - 1)){
                x = 0;
                y++;
            }
            else{
                x++;
            }
        }
    }
    return newImage;
};

2. Use Opencv, Test the resolution and frame rate of your computer camera

It should be noted that opencv4 Identifier not defined in CV_CAP_PROP_FPS;CV_CAP_PROP_FRAME_COUNT;CV_CAP_PROP_POS_FRAMES problem , because opencv Version update too fast ,opencv4 Many identifiers have changed in , Make the following changes to the following three identifiers ：

CV_CAP_PROP_FPS   ->    CAP_PROP_FPS
CV_CAP_PROP_FRAME_COUNT ->  CAP_PROP_FRAME_COUNT
CV_CAP_PROP_POS_FRAMES ->  CAP_PROP_POS_FRAMES

And if not defined before cv In terms of namespace （using namespace cv;） It is necessary to use cv::CAP_PROP_FRAME_COUNT This format .

#include <stdlib.h>
#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include "opencv2/imgproc/imgproc.hpp"
int main(int argc, const char** argv)
{
    cv::Mat frame;
    //  You can input video streams from the camera or play video files directly 
    cv::VideoCapture capture(0);
    //    cv::VideoCapture capture("vedio1.avi");
    double fps;
    char string[10]; 
    cv::namedWindow("Camera FPS");
    double t = 0;
    while (1)
    {
        t = (double)cv::getTickCount();
        if (cv::waitKey(1) == 27) { break; }          //#if (cv::waitKey(100) == 27) { break; }
        if (capture.isOpened())
        {
            capture >> frame;
          
            t = ((double)cv::getTickCount() - t) / cv::getTickFrequency();
            fps = 1.0 / t;
            sprintf_s(string, "%.2f", fps);      
            std::string fpsString("FPS:");
            fpsString += string;                    
            printf("fps: %.2f width:%d height:%d fps:%.2f\n", fps, frame.cols, frame.rows, capture.get(cv::CAP_PROP_FPS));
            
            cv::putText(frame, //  Image matrix 
                fpsString,                  
                cv::Point(5, 20),           
                cv::FONT_HERSHEY_SIMPLEX,   
                0.5, 
                cv::Scalar(0, 0, 0));       
            cv::imshow("Camera FPS", frame);
        }
        else
        {
            std::cout << "No Camera Input!" << std::endl;
            break;
        }
    }
}

3. Take an image of yourself from the outside with a computer camera , Add circle （ Or other graphics ） Code yourself , At the same time, you can change the resolution by pressing the key , And add time in the lower right corner of the picture

The original title is to code with pictures , Press the key to change the resolution, but my code always has bug, So I did a facial treatment , Set up ROI after , You can operate the area as a whole . This code will a region of interest A Assign a value to a variable B after , This variable can be B Assign to another area C, So as to achieve in the area C Copy area within A Purpose .
 

import cv2 
import numpy as np

cap = cv2.VideoCapture(0) 

ret,frame = cap.read()

cv2.imshow('cap',frame)

cv2.waitKey()
cv2.destroyAllWindows()

lena=cv2.imread("lena.bmp",0)
h,w=lena.shape
mask=np.zeros((h,w),dtype=np.uint8)
mask[220:400,250:350]=1
key=np.random.randint(0,256,size=[h,w],dtype=np.uint8) 

lenaXorKey=cv2.bitwise_xor(lena,key)  
encryptFace=cv2.bitwise_and(lenaXorKey,mask*255) 
noFace1=cv2.bitwise_and(lena,(1-mask)*255) 
maskFace=encryptFace+noFace1               
extractFace=cv2.bitwise_and(extractOriginal,mask*255)  
noFace2=cv2.bitwise_and(maskFace,(1-mask)*255)  
extractLena=noFace2+extractFace   


cv2.imshow("lena",lena)
cv2.imshow("mask",mask*255)          
cv2.imshow("1-mask",(1-mask)*255)
cv2.imshow("key",key)
cv2.imshow("lenaXorKey",lenaXorKey)
cv2.imshow("encryptFace",encryptFace)
cv2.imshow("noFace1",noFace1)
cv2.imshow("maskFace",maskFace)
cv2.imshow("extractOriginal",extractOriginal)
cv2.imshow("extractFace",extractFace)
cv2.imshow("noFace2",noFace2)
cv2.imshow("extractLena",extractLena)
cv2.waitKey()
cv2.destroyAllWindows()

3、 ... and 、 Exercises （python Realization ）

1. Display two pictures with different resolutions at the same time , Compare their size

#include <opencv2/opencv.hpp>
#include <iostream>
#include <string>
 
using namespace cv;
int main() {
    Mat img  = imread(" Your path 1" , 1);
    Mat img1 = imread(" Your path 2" , 1);
    printf(" chart 1 The resolution is :%dx%d\n", img.cols, img.rows);
    printf(" chart 2 The resolution is :%dx%d", img1.cols, img1.rows);
    return 0;
}

2. Use Opencv, Test the resolution and frame rate of your computer camera

#include <opencv2/opencv.hpp>
#include <iostream>
#include <string>
 
using namespace cv;
int main() {
    VideoCapture capture;
    Mat frame;
    frame= capture.open(" Your path ");
    int fps = capture.get(CAP_PROP_FPS);
    int width = capture.get(CAP_PROP_FRAME_WIDTH);
    int height = capture.get(CAP_PROP_FRAME_HEIGHT);
    namedWindow("output", WINDOW_AUTOSIZE);
    while (capture.read(frame))
    {
        imshow("output", frame);
        char ch = waitKey(30);
        if(ch == 27){
            break;
        }
    }
    printf("FPS:%d\n", fps);
    printf(" This resolution is %dx%d",width ,height);
    capture.release();
    return 0;
}

3. Take an image of yourself from the outside with a computer camera , Add circle （ Or other graphics ） Code yourself , At the same time, you can change the resolution by pressing the key , And add time in the lower right corner of the picture

#include <opencv2/opencv.hpp>
#include <iostream>
#include <string>
using namespace cv;
using namespace std;
 
 
int main() {
    double scale_up_x = 1.0;
    double scale_up_y = 1.0;
    int i = 1;
    Mat scaled_f_up, scaled_f_down;
    while(i){
        auto t = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
        std::stringstream ss;
        ss << std::put_time(std::localtime(&t), "%Y-%m-%d-%H:%M:%S");
        std::string str_time = ss.str();
 
        Mat pic = imread("/Users/milkman/Desktop/pic1.jpg", 1);
        if (pic.empty())  
        {
            std::cout << " Read failed " << std::endl;
            return -1;
        }
        Point p1(900, 900);
        putText(pic, "milkman", p1, FONT_HERSHEY_COMPLEX, 2, cv::Scalar(0, 0, 0), 3, 8, 0);
        char time = system("time");
        putText(pic, str_time, Point(1000, 700), FONT_HERSHEY_COMPLEX, 1, cv::Scalar(0, 0, 0), 3, 8, 0);
        rectangle(pic, Point(579, 290), Point(815, 622), cv::Scalar(255, 255, 255), -1);
        imshow("test", pic);
        waitKey(0);
        char ch = waitKey(0);
        if(ch == 38){
            scale_up_x += 0.1;
            resize(pic, scaled_f_up, Size(), scale_up_x, scale_up_y, INTER_LINEAR);
            imshow("scaled_f_up", scaled_f_up);
            waitKey(0);
        }
        if(ch == 40){
            scale_up_y -= 0.1;
            resize(pic, scaled_f_up, Size(), scale_up_x, scale_up_y, INTER_LINEAR);
            imshow("scaled_f_up", scaled_f_up);
            waitKey(0);
        }
        if(ch == 27){
            break;
        }
        scanf("%d", &i);
    }
    return 0;
}
//python
#mport cv2
import numpy as np

image = cv2.imread('image.jpg')
cv2.imshow('Original Image', image)

down_width = 300
down_height = 200
down_points = (down_width, down_height)
resized_down = cv2.resize(image, down_points, interpolation= cv2.INTER_LINEAR)

up_width = 600
up_height = 400
up_points = (up_width, up_height)
resized_up = cv2.resize(image, up_points, interpolation= cv2.INTER_LINEAR)

cv2.imshow('Resized Down by defining height and width', resized_down)
cv2.waitKey()
cv2.imshow('Resized Up image by defining height and width', resized_up)
cv2.waitKey()
//
//C++
#include<opencv2/opencv.hpp>
#include<iostream>

using namespace std;
using namespace cv;

int main()
{
	Mat image = imread("image.jpg");
	imshow("Original Image", image);

	int down_width = 300;
	int down_height = 200;
	Mat resized_down;
	resize(image, resized_down, Size(down_width, down_height), INTER_LINEAR);
	int up_width = 600;
	int up_height = 400;
	Mat resized_up;
	resize(image, resized_up, Size(up_width, up_height), INTER_LINEAR)
	imshow("Resized Down by defining height and width", resized_down);
	waitKey();
	imshow("Resized Up image by defining height and width", resized_up);
	waitKey();


	destroyAllWindows();
	return 0;
}
//
//cv2.destroyAllWindows() or destroyAllWindows(); end //

The learning

opencv The function is realized with C++ Than python fast , But it is more difficult than python Much larger . I think my code should not be the simplest and most efficient , So please correct any mistakes , There are also some ideas that may not change very well , The premise of writing good code is to be solid in the basic skills of programming language , I hope I can learn more and write more code , Let my code mature slowly , And beginner opencv Some knowledge is really difficult , You can check it out B Station video and so on .