Как на winapi наложить оверлей с прозрачным фоном на окно програмы

 #include <windows.h> 
 
const char CLASS_NAME[] = "OverlayWindow"; 
HBITMAP hBitmap = NULL; 
 
HWND CreateOverlayWindow(HINSTANCE hInstance, int x, int y, int width, int height) { 
    WNDCLASS wc = {}; 
    wc.lpfnWndProc = DefWindowProc; 
    wc.hInstance = hInstance; 
    wc.lpszClassName = CLASS_NAME; 
 
    RegisterClass(&wc); 
 
    HWND hwnd = CreateWindowEx( 
        WS_EX_LAYERED | WS_EX_TOPMOST | WS_EX_TRANSPARENT, 
        CLASS_NAME, 
        "Overlay", 
        WS_POPUP, 
        x, y, 
        width, height, 
        NULL, NULL, 
        hInstance, 
        NULL 
    ); 
 
    SetLayeredWindowAttributes(hwnd, RGB(0, 0, 0), 0, LWA_COLORKEY); 
    return hwnd; 
} 
 
void LoadImageResource() { 
    hBitmap = (HBITMAP)LoadImage(NULL, "path_to_your_image.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE); 
} 
 
LRESULT CALLBACK OverlayProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { 
    switch (uMsg) { 
        case WM_PAINT: { 
            PAINTSTRUCT ps; 
            HDC hdc = BeginPaint(hwnd, &ps); 
 
            if (hBitmap) { 
                HDC hMemDC = CreateCompatibleDC(hdc); 
                SelectObject(hMemDC, hBitmap); 
 
                BITMAP bitmap; 
                GetObject(hBitmap, sizeof(bitmap), &bitmap); 
 
                BitBlt(hdc, 0, 0, bitmap.bmWidth, bitmap.bmHeight, 
                       hMemDC, 0, 0, SRCCOPY); 
 
                DeleteDC(hMemDC); 
            } 
 
            EndPaint(hwnd, &ps); 
            return 0; 
        } 
        case WM_DESTROY: 
            DeleteObject(hBitmap); 
            PostQuitMessage(0); 
            return 0; 
    } 
    return DefWindowProc(hwnd, uMsg, wParam, lParam); 
} 
 
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE, LPSTR, int) { 
    LoadImageResource(); 
    HWND overlay = CreateOverlayWindow(hInstance, 100, 100, 400, 300); 
    SetWindowLongPtr(overlay, GWLP_WNDPROC, (LONG_PTR)OverlayProc); 
    ShowWindow(overlay, SW_SHOW); 
    UpdateWindow(overlay); 
 
    MSG msg; 
    while (GetMessage(&msg, NULL, 0, 0)) { 
        TranslateMessage(&msg); 
        DispatchMessage(&msg); 
    } 
 
    return 0; 
}