OPENCV Desktop Capture

Question

How to capture the desktop in OpenCV (ie. turn a bitmap into a Mat)?

Hello,

Can anyone explain to me how I would use this code in OpenCV to capture the deskt

Answer 1

I would make hwnd2mat a little bit more specific and address Stepan Yakovenko's comment by adding definition and references to "valueOfChangeTheSizeOfTextAppsAndOtherItemsInWindowsDisplaySettings".

Mat hwnd2mat(HWND hwnd)
{
     HDC hwindowDC,hwindowCompatibleDC;

     int height,width,srcheight,srcwidth;
     HBITMAP hbwindow;
     Mat src;
     BITMAPINFOHEADER  bi;

     hwindowDC=GetDC(hwnd);
     hwindowCompatibleDC=CreateCompatibleDC(hwindowDC);
     SetStretchBltMode(hwindowCompatibleDC,COLORONCOLOR);

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

     float valueOfChangeTheSizeOfTextAppsAndOtherItemsInWindowsDisplaySettings = 1.5;
     srcheight = (int)((float)windowsize.bottom * valueOfChangeTheSizeOfTextAppsAndOtherItemsInWindowsDisplaySettings);
     srcwidth = (int)((float)windowsize.right * valueOfChangeTheSizeOfTextAppsAndOtherItemsInWindowsDisplaySettings);
     height = windowsize.bottom/1;  //change this to whatever size you want to resize to
     width = windowsize.right/1;

     src.create(height,width,CV_8UC4);

     // create a bitmap
     hbwindow = CreateCompatibleBitmap( hwindowDC, width, height);
     bi.biSize = sizeof(BITMAPINFOHEADER);    //http://msdn.microsoft.com/en-us/library/windows/window/dd183402%28v=vs.85%29.aspx
     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 = 0;
     bi.biYPelsPerMeter = 0;
     bi.biClrUsed = 0;
     bi.biClrImportant = 0;

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

     // avoid memory leak
     DeleteObject (hbwindow);
     DeleteDC(hwindowCompatibleDC);
     ReleaseDC(hwnd, hwindowDC);

     return src;
 }