删除HBITMAP会在运行时导致访问冲突

我有以下代码来截取一个窗口的屏幕截图,并获取其中特定像素的颜色:

void ProcessScreenshot(HWND hwnd){

HDC WinDC;
HDC CopyDC;
HBITMAP hBitmap;
RECT rt;

GetClientRect (hwnd, &rt);
WinDC = GetDC (hwnd);
CopyDC = CreateCompatibleDC (WinDC);

//Create a bitmap compatible with the DC
hBitmap = CreateCompatibleBitmap (WinDC,
    rt.right - rt.left, //width
    rt.bottom - rt.top);//height

SelectObject (CopyDC, hBitmap);

BitBlt (CopyDC,   //destination
    0,0,
    rt.right - rt.left, //width
    rt.bottom - rt.top, //height
    WinDC,    //source
    0, 0,
    SRCCOPY);       

COLORREF col = ::GetPixel(CopyDC,145,293);

// Do some stuff with the pixel colour.... 

delete hBitmap;

ReleaseDC(hwnd, WinDC);
ReleaseDC(hwnd, CopyDC);

}

行“delete hBitmap;”导致运行时错误:访问冲突。我想我不能就这样删除它?

因为位图占用了很多空间,如果我不把它处理掉,我最终会导致巨大的内存泄漏。我的问题是:发布DC-HBITMAP是为了解决这个问题,还是在我发布DC之后它仍然存在?如果是后者,我如何正确地摆脱HBITMAP?