OpenCV imwrite无效

Question

我有一个简单的OpenCV应用程序，它从网络摄像头获取视频流，当按下spacebar时，它会捕获当前图像并冻结该图像。当我尝试使用cv::imwrite()方法将图片保存到磁盘时，它不起作用。代码成功编译但不保存图像。它也会从通话中返回错误值。我不确定这是一个图像类型或其他类型的问题，但我似乎很难过。

以下是我当前cpp类的代码：

#include <iostream>

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"

using namespace std;
using namespace cv;

Mat picture;
char key;

class FacialRec {

};

int main() {
    //Starting the video
    VideoCapture videoCapture(0);

    if (!videoCapture.isOpened()) {
        cout << "Unable to open video file." << endl;
        return 1;
    }

    namedWindow("Webcam", CV_WINDOW_AUTOSIZE);

    while(true) {
        Mat frame;
        videoCapture.retrieve(frame);
        bool success = videoCapture.read(frame);

        if (!success) {
            cout << "Could not read from video file" << endl;
            return 1;
        }

        imshow("Webcam", frame);
        key = waitKey(30);

        if (key == 27) { //escape key pressed: stop program
            cout << "ESC pressed. Program closing..." << endl;
            break;
        }else if (key == ' ') { //spacebar pressed: take a picture
            picture = frame;
            key = -1;

            while (true) {
                imshow("Webcam", picture);

                key = waitKey(30);

                if (key == 27 || key == 32) {
                    cout << "ESC or SPACE pressed. Returning to video..." << endl;
                    break;
                }

                if (key == 115) {
                    //trying to save to current directory
                    bool maybe = imwrite("/testimage.jpg", picture);
                    // maybe bool is always getting value of 0, or false
                   cout << "s was pressed. saving image " << maybe << endl;
                }   
            }
        }

    }

    return 0;
}

Answer 1

您正在尝试将testimage.jpg写入/目录。执行程序可能没有足够的权限写入该目录。根据您的评论，您可能想要

//trying to save to current directory
bool maybe = imwrite("./testimage.jpg", picture);

由于.表示当前工作目录。

Answer 2

OpenCV有时会遇到写入.jpg图片的问题。尝试将其更改为.png或.bmp，看看是否会对您的情况产生影响。

如果您在编写图像时遇到其他问题，可以在OpenCV中调试它们，方法是添加以下几行代码来显示它们，看看它们是否有效：

// Create a window for display.
namedWindow( "Display window", WINDOW_AUTOSIZE );

// Show our image inside it.
imshow( "Display window", picture );                   

// Wait for a keystroke in the window
waitKey(0);                                         

Answer 3

一些建议。

1. 尝试不同的文件格式。
2. 您的IDE是否知道您的目标文件夹/主路径目录？
3. 你的形象绝对有效吗？当你imshow（）时它会显示吗？