OpenCV3读取、写入和保存图像

需要说明的是在OpenCV3中已经将imread()和imwrite()函数转移到imgcodecs模块中，因此读写图像时，需要包含imgcodecs.hpp头文件，但是highgui.hpp头文件中已经包含了该头文件，因此不用再显式包含了。

#include <iostream>
#include <string>
using namespace std;

// OpenCV includes
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;

int main(int argc, const char** argv)
{
    // Read images
    Mat color = imread("../images/eating.jpg");
    Mat gray  = imread("../images/eating.jpg", 0);

    // Write images
    imwrite("gray.jpg", gray);

    // Get same pixel with opencv function
    int myRow = color.cols - 1;
    int myCol = color.rows - 1;
    Vec3b pixel = color.at<Vec3b>(myRow, myCol);
    cout << "Pixel Value (B, G, R): ("
         << (int)pixel[0] << ", "
         << (int)pixel[1] << ", "
         << (int)pixel[2] << ")" << endl;

    // Show images
    imshow("Color Image", color);
    imshow("Gray Image", gray);

    // Wait for any key
    waitKey(0);
    return 0;
}

显示的图片效果如下：