Video recording of the window on OpenCV C++

I’m new to using OpenSv. I am trying to write a program for recording windows, but for some reason after the program finishes, I get a corrupted .avi file. It seems that I do all the actions correctly. I don’t understand what the problem is. The hwnd2mat() and windowNames() functions work correctly, the error is clearly not in it. The code looks massive, but in fact, most of the code is occupied by the translation of the image from the HWND to the Mat.

#include <iostream>
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <opencv2/videoio.hpp>
#include <Windows.h>

BOOL CALLBACK windowNames(HWND hwnd, LPARAM lParam) {
	const DWORD TITLE_SIZE = 1024;
	WCHAR windowTitle[TITLE_SIZE];

	GetWindowTextW(hwnd, windowTitle, TITLE_SIZE);

	int length = ::GetWindowTextLength(hwnd);
	std::wstring title(&windowTitle[0]);
	if (!IsWindowVisible(hwnd) || length == 0 || title == L"Program Manager") {
		return TRUE;

	// Retrieve the pointer passed into this callback, and re-'type' it.
	// The only way for a C API to pass arbitrary data is by means of a void*.
	std::vector<std::wstring>& titles = *reinterpret_cast<std::vector<std::wstring>*>(lParam);

	return TRUE;

cv::Mat hwnd2mat(HWND hwnd)
	HDC hwindowDC, hwindowCompatibleDC;

	int height, width, srcheight, srcwidth;
	HBITMAP hbwindow;
	cv::Mat src;
	hwindowDC = GetDC(hwnd);
	hwindowCompatibleDC = CreateCompatibleDC(hwindowDC);
	SetStretchBltMode(hwindowCompatibleDC, COLORONCOLOR);

	RECT windowsize;    // get the height and width of the screen
	GetClientRect(hwnd, &windowsize);

	srcheight = windowsize.bottom;
	srcwidth = windowsize.right;
	height = windowsize.bottom / 1;  //change this to whatever size you want to resize to
	width = windowsize.right / 1;

	// create a bitmap
	hbwindow = CreateCompatibleBitmap(hwindowDC, width, height);
	bi.biSize = sizeof(BITMAPINFOHEADER);    //
	bi.biWidth = width;
	bi.biHeight = -height;  //this is the line that makes it draw upside down or not
	bi.biPlanes = 1;
	bi.biBitCount = 32;
	bi.biCompression = BI_RGB;
	bi.biSizeImage = 0;
	bi.biXPelsPerMeter = 1;
	bi.biYPelsPerMeter = 2;
	bi.biClrUsed = 3;
	bi.biClrImportant = 4;

	// use the previously created device context with the bitmap
	SelectObject(hwindowCompatibleDC, hbwindow);
	// copy from the window device context to the bitmap device context
	StretchBlt(hwindowCompatibleDC, 0, 0, width, height, hwindowDC, 0, 0, srcwidth, srcheight, SRCCOPY); //change SRCCOPY to NOTSRCCOPY for wacky colors !

	src.create(height, width, CV_8UC4);
	GetDIBits(hwindowCompatibleDC, hbwindow, 0, height,, (BITMAPINFO*)&bi, DIB_RGB_COLORS);  //copy from hwindowCompatibleDC to hbwindow

	// avoid memory leak
	ReleaseDC(hwnd, hwindowDC);

	return src;

int main(int argc, char** argv)
	std::vector<std::wstring> titles; // we use std::wstring in place of std::string. This is necessary so that the entire character set can be represented.
	EnumWindows(windowNames, reinterpret_cast<LPARAM>(&titles));
	HWND hwndDesktop = GetDesktopWindow();
	size_t number = 0;
	int i = 0;
	for (const auto& title : titles)
		std::wcout << L"Title: " << i++ << title << std::endl;
	std::cin >> number;
	HWND hwndWindow = FindWindow(NULL, titles[number].c_str());
	cv::namedWindow("output", cv::WINDOW_NORMAL);
	cv::Mat src = hwnd2mat(/*hwndDesktop*/hwndWindow);
	cv::VideoWriter outputVideo("output.avi", cv::VideoWriter::fourcc('M', 'J', 'P', 'G'), 1, cv::Size(src.cols, src.rows));
	int key = 0;
	while (key != 27)
		 src = hwnd2mat(hwndWindow);
		cv::imshow("output", src);
		key = cv::waitKey(60); //press ESC to end
	return 0;

take a look at this i think you need to convert BGRA to BGR


Thank you. It’s help. Could you answer on one more question? So, when I try to capture Google Chrome, I only get a black image. What could be the reason for this? Is this some kind of Google Chrome protection or what?