Calling getdc getpixel function in chrome browser

class FindWin
{
public:
    FindWin( PCSTR text, bool partial=true );

    // can be overridden to do something to the window found

    virtual bool Find()
    {
        m_Found = false;
        if( m_Text && * m_Text )
            EnumWindows( EnumFunc, (LPARAM)this );
        return m_Found;
    }

    // return a handle to the window found

    HWND        GetWnd()        { return m_hWnd; }

protected:
    BOOL        Matches( HWND hwnd, PCSTR wintext );

    static BOOL CALLBACK EnumFunc( HWND hwnd, LPARAM lParam );

protected:
    PCSTR       m_Text          { nullptr };
    size_t      m_Length        { 0 };
    HWND        m_hWnd          { NULL };
    bool        m_Found         { false };
    bool        m_Partial       { false };      // allowing partial match
};

///////////////////////////////////////////////////////////////////////

FindWin::FindWin( PCSTR text, bool partial )
{
    m_Text = text;
    m_Length = strlen( m_Text );
    m_Partial = partial;
}

///////////////////////////////////////////////////////////////////////

BOOL FindWin::Matches( HWND hwnd, PCSTR wintext )
{
    if( m_Partial )
        m_Found = strncmp( wintext, m_Text, m_Length ) == 0;
    else
        m_Found = strcmp( wintext, m_Text ) == 0;
    
    if( m_Found )
        m_hWnd = hwnd;
    return (int) ! m_Found;     // return false if found
}

///////////////////////////////////////////////////////////////////////

BOOL CALLBACK FindWin::EnumFunc( HWND hwnd, LPARAM lParam )
{
    FindWin * pew = (FindWin *)lParam;
    char wtext[ MAX_PATH+4 ] = { 0 };
    GetWindowText( hwnd, wtext, MAX_PATH );
    return pew->Matches( hwnd, wtext );
}

void ReadPixelValue()
{
    FindWin finder( "Microsoft Spy++" );
    if( ! finder.Find() )
    {
        printf( "Error - unable to find window\n" );
        return;
    }

    HWND hwnd = finder.GetWnd();
    HDC hdc = ::GetDC( hwnd );
    if( ! hdc )
    {
        printf( "Error - unable to obtain device context\n" );
        return;
    }

    COLORREF color = GetPixel( hdc, 20, 20 );

    printf( "pixel color is %06X\n", color );
}