python

# -*- coding: utf-8 -*-
import cv2 as cv
import numpy as np
def function():
    img = cv.imread("./image.jpg")
    cv.namedWindow("input", cv.WINDOW_AUTOSIZE)
    cv.imshow("input", img)
    gray_img = cv.cvtColor(img, cv.COLOR_BGR2GRAY)
    cv.namedWindow("gray_image", cv.WINDOW_AUTOSIZE)
    cv.imshow("gray_image", gray_img)
    img1 = np.copy(img)
    img2 = img
    #虽然是在赋值后才做的修改，但是还是会影响img2
    img[100: 200, 200: 300, :] = 0
    cv.imshow("fuzhi", img2)
    cv.imshow("xiugaixiangsu", img)
    img3 = np.zeros(img.shape, img.dtype)
    cv.imshow("np.zeros", img3)
    img4 = np.ones(shape = [512, 512, 3], dtype = np.uint8)
    img4[:, :, 0] = 255
    cv.imshow("np.ones, B_channel=255", img4)
    img5 = np.zeros([512, 512], np.uint8)
    cv.imshow("erweishape", img5)
    
function()
cv.waitKey(0)
cv.destroyAllWindows()

c++

和Python中使用numpy作为图片的容器不同，c++中目前使用Mat类型作为image的容器（OpenCV2.x之前为IplImage，它需要程序员自己管理内存），Mat类型的结构为：一个表示图片信息的矩阵头和一个指向存储图片数据的矩阵的指针。基于这个结构c++中给新Mat值时，赋值操作（=）和拷贝构造函数（Mat img1(img)）仅仅复制矩阵头，而新旧Mat指向同一个图片矩阵，所以这种方式比较节省时间；而clone()和copyTo()需要复制矩阵头和图片矩阵，所以比较费时间

#include <opencv2/opencv.hpp>
#include <iostream>
using namespace std;
using namespace cv;
int main() {
    Mat img = imread("E:\\varietyShop\\bjut\\study\\knowledgePlanet\\image.jpg");
    imshow("input", img);
    //克隆
    Mat img_copy = img.clone();
    //赋值
    Mat img_give = img;
    //复制
    Mat img_copyto;
    img.copyTo(img_copyto);
    imshow("copy", img_copyto);
    //拷贝构造函数
    Mat img4(img);

    Mat img1 = Mat::zeros(img.size(), img.type());
    Mat img2 = Mat::zeros(Size(512, 512), CV_8UC3);
    Mat img3 = Mat::ones(Size(512, 512), CV_8UC3);
    Mat kernal = (Mat_<char>(3, 3) << 0, -1, 0, -1, 5, -1, 0, -1, 0);
    
    waitKey(0);
    return 0;
}