I use this standard sample to grab screen with opencv. It works correctly if my font size in control panel is 100%:
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);
srcheight = windowsize.bottom;
srcwidth = windowsize.right;
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;
SelectObject(hwindowCompatibleDC, hbwindow);
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
DeleteObject(hbwindow);
DeleteDC(hwindowCompatibleDC);
ReleaseDC(hwnd, hwindowDC);
return src;
}
int main() {
HWND hwndDesktop = GetDesktopWindow();
Mat src = hwnd2mat(hwndDesktop);
imwrite("output.bmp", src);
return 0;
}
But if I enable large fonts (on Windows 10 at least), then it gives me only upper left corner of the screen:
how can I fix that?
Another solution might be calling SetProcessDPIAware() in the beginning of your program. Helped me.