#include <windows.h>
#include <vector>
#include <chrono>
#include <numeric>

int main()
{
    std::vector<unsigned long long> times(40);
    HDC hdcScreen = ::GetDC(HWND_DESKTOP);
    HDC hdcShot = ::CreateCompatibleDC(hdcScreen);
    int cx = GetDeviceCaps(hdcScreen, HORZRES);
    int cy = GetDeviceCaps(hdcScreen, VERTRES);
    HGDIOBJ hbmpShot = ::CreateCompatibleBitmap(hdcScreen, cx, cy);
    hbmpShot = SelectObject(hdcShot, hbmpShot);
    for( size_t i = times.size(); i--; ) {
        auto start = std::chrono::high_resolution_clock::now();
        ::BitBlt(hdcShot, 0, 0, cx, cy, hdcScreen, 0, 0, SRCCOPY);
        auto finish = std::chrono::high_resolution_clock::now();
        times[i] = std::chrono::duration_cast<std::chrono::milliseconds>(finish - start).count();
    }
    ::ReleaseDC(HWND_DESKTOP, hdcScreen);
    hbmpShot = SelectObject(hdcShot, hbmpShot);
    ::DeleteObject(hbmpShot);
    ::DeleteDC(hdcShot);
    printf("Time: %f\n", double(std::accumulate(times.begin(), times.end(), (unsigned long long)0)) / times.size());
    return 0;
}