如何在 MFC 窗口中输出 cv::Mat

Question

I have 2 programs, MFC program and OpenCV. How I should to unite programs? How output cv::Mat in MFC window? What MFC widget I should be use? How I should convert cv::Mat to MFC widgets?

MFC program:

#include <afxwin.h> 

        class CMyMainWnd : public CFrameWnd
        {
        public:
            CMyMainWnd() { Create(NULL, L"My title"); }
        };

        class CMyApp : public CWinApp
        {
        public:
            CMyApp() {};
            virtual BOOL InitInstance() {
                m_pMainWnd = new CMyMainWnd();
                m_pMainWnd->ShowWindow(SW_SHOW);
                return TRUE;
            }
        };

        CMyApp theApp;

OpenCV program:

#include "opencv2/opencv.hpp"
#include <iostream>

using namespace std;
using namespace cv;

int main() {

    VideoCapture cap(0);

    while (1) {

        Mat frame;
        cap >> frame;

        if (frame.empty())
            break;

        imshow("Frame", frame);

        char c = (char)waitKey(25);
        if (c == 27)
            break;
    }

    cap.release();

    destroyAllWindows();

    return 0;
}

Answer 1

Your main example differs in that it doesn't directly create any window. It lets opencv create the window.

To duplicate that example, simply move the opencv loop in to CWinApp::InitInstance and don't create a separate MFC window.

To unite opencv with MFC, use opencv to grab the video frame, and draw the frame on MFC window.

CWinApp::OnIdle can be used to continuously update the window. opencv's frame includes the bitmap bits, these bits can be copied directly to MFC windows's HDC using SetDIBitsToDevice or similar functions.

class CMyMainWnd : public CFrameWnd
{
    cv::VideoCapture video;
public:
    CMyMainWnd()
    {
        video.open(0);
    }

    void CMyMainWnd::OnPaint()
    {
        CPaintDC dc(this);

        cv::Mat mat;
        video >> mat;
        if(mat.empty())
            return;

        BITMAPINFOHEADER bi = { sizeof(bi) };
        bi.biWidth = mat.cols;
        bi.biHeight = -mat.rows;
        bi.biBitCount = (WORD)(mat.channels() * 8);
        bi.biPlanes = 1;

        SetDIBitsToDevice(dc, 0, 0, mat.cols, mat.rows, 0, 0, 0, mat.rows,
            mat.data, (BITMAPINFO*)&bi, DIB_RGB_COLORS);
    }

    DECLARE_MESSAGE_MAP()
};

BEGIN_MESSAGE_MAP(CMyMainWnd, CWnd)
    ON_WM_PAINT()
END_MESSAGE_MAP()

class CMyApp : public CWinApp
{
public:
    virtual BOOL InitInstance()
    {
        CWinApp::InitInstance();
        CMyMainWnd *wnd = new CMyMainWnd();
        m_pMainWnd = wnd;
        wnd->Create(NULL, L"My title");
        wnd->ShowWindow(SW_SHOW);
        return TRUE;
    }

    BOOL OnIdle(LONG lCount)
    {
        CWinApp::OnIdle(lCount);
        m_pMainWnd->Invalidate(FALSE);
        return TRUE;
    }
};

CMyApp theApp;