为什么 Windows 服务中的打印屏幕返回黑色图像？

Question

protected override void OnStart(string[] args)
{
    base.OnStart(args);
    CaptureScreen();

}

protected override void OnStop()
{
    base.OnStop();

}

private void CaptureScreen()
{

    Bitmap printscreen = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);

    Graphics graphics = Graphics.FromImage(printscreen as Image);

    graphics.CopyFromScreen(0, 0, 0, 0, printscreen.Size);

    printscreen.Save(@"L:\" + Counter++ + ".jpg", ImageFormat.Jpeg);
}

• 我检查了与桌面的交互，
• 尝试了 localService 帐户 &用户

Answer 1

这是 Vista 中添加的会话 0 隔离功能的一部分。服务现在使用自己的工作站和桌面运行自己的会话。与运行登录提示和屏幕保护程序的会话非常相似。您正在对该会话的桌面进行屏幕截图，其中没有任何内容。无法再访问用户桌面。这是一项安全功能，可以防止粉碎攻击。诚然，我不明白为什么“与桌面交互”复选框没有被删除。

您需要将程序更改为作为“Windows 应用程序”运行，而不是作为服务运行。将快捷方式放入“启动”文件夹中或使用“运行”注册表项。没关系，当没有用户登录时，没有什么值得抓拍的。

Answer 2

您需要将服务设置为用户 Windows Station。这不是我的代码，我不记得从哪里得到它。
添加这两个类
然后你可以创建一个 Desktop 对象

Desktop userDesk = new Desktop();

然后，当您需要服务与用户会话交互时，您可以编写

userDesk.BeginInteraction();

最后要返回到您的服务会话，您可以调用

userDesk.EndInteraction();

internal class Desktop
{
    private IntPtr m_hCurWinsta = IntPtr.Zero;
    private IntPtr m_hCurDesktop = IntPtr.Zero;
    private IntPtr m_hWinsta = IntPtr.Zero;
    private IntPtr m_hDesk = IntPtr.Zero;

    /// <summary>
    /// associate the current thread to the default desktop
    /// </summary>
    /// <returns></returns>
    internal bool BeginInteraction()
    {
        EndInteraction();
        m_hCurWinsta = User32DLL.GetProcessWindowStation();
        if (m_hCurWinsta == IntPtr.Zero)
            return false;

        m_hCurDesktop = User32DLL.GetDesktopWindow();
        if (m_hCurDesktop == IntPtr.Zero)
            return false;

        m_hWinsta = User32DLL.OpenWindowStation("winsta0", false,
            WindowStationAccessRight.WINSTA_ACCESSCLIPBOARD |
            WindowStationAccessRight.WINSTA_ACCESSGLOBALATOMS |
            WindowStationAccessRight.WINSTA_CREATEDESKTOP |
            WindowStationAccessRight.WINSTA_ENUMDESKTOPS |
            WindowStationAccessRight.WINSTA_ENUMERATE |
            WindowStationAccessRight.WINSTA_EXITWINDOWS |
            WindowStationAccessRight.WINSTA_READATTRIBUTES |
            WindowStationAccessRight.WINSTA_READSCREEN |
            WindowStationAccessRight.WINSTA_WRITEATTRIBUTES
            );
        if (m_hWinsta == IntPtr.Zero)
            return false;

        User32DLL.SetProcessWindowStation(m_hWinsta);

        m_hDesk = User32DLL.OpenDesktop("default", OpenDesktopFlag.DF_NONE, false,
                DesktopAccessRight.DESKTOP_CREATEMENU |
                DesktopAccessRight.DESKTOP_CREATEWINDOW |
                DesktopAccessRight.DESKTOP_ENUMERATE |
                DesktopAccessRight.DESKTOP_HOOKCONTROL |
                DesktopAccessRight.DESKTOP_JOURNALPLAYBACK |
                DesktopAccessRight.DESKTOP_JOURNALRECORD |
                DesktopAccessRight.DESKTOP_READOBJECTS |
                DesktopAccessRight.DESKTOP_SWITCHDESKTOP |
                DesktopAccessRight.DESKTOP_WRITEOBJECTS
                );
        if (m_hDesk == IntPtr.Zero)
            return false;

        User32DLL.SetThreadDesktop(m_hDesk);

        return true;
    }

    /// <summary>
    /// restore
    /// </summary>
    internal void EndInteraction()
    {
        if (m_hCurWinsta != IntPtr.Zero)
            User32DLL.SetProcessWindowStation(m_hCurWinsta);

        if (m_hCurDesktop != IntPtr.Zero)
            User32DLL.SetThreadDesktop(m_hCurDesktop);

        if (m_hWinsta != IntPtr.Zero)
            User32DLL.CloseWindowStation(m_hWinsta);

        if (m_hDesk != IntPtr.Zero)
            User32DLL.CloseDesktop(m_hDesk);
    }
}
public static class User32DLL
{
    /// <summary>
    /// The GetDesktopWindow function returns a handle to the desktop window. 
    /// The desktop window covers the entire screen. 
    /// The desktop window is the area on top of which other windows are painted. 
    /// </summary>
    /// <returns>The return value is a handle to the desktop window. </returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr GetDesktopWindow();


    /// <summary>
    /// Retrieves a handle to the current window station for the calling process.
    /// </summary>
    /// <returns>If the function succeeds,
    /// the return value is a handle to the window station.
    /// If the function fails, the return value is NULL.</returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr GetProcessWindowStation();


    /// <summary>
    /// Retrieves a handle to the desktop assigned to the specified thread.
    /// </summary>
    /// <param name="dwThread">[in] Handle to the thread
    ///     for which to return the desktop handle.</param>
    /// <returns>If the function succeeds, the return value is a handle to the 
    /// desktop associated with the specified thread. 
    /// If the function fails, the return value is NULL.</returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr GetThreadDesktop(uint dwThread);


    /// <summary>
    /// Opens the specified window station.
    /// </summary>
    /// <param name="lpszWinSta">Pointer to a null-terminated
    ///           string specifying the name of the window station 
    /// to be opened. Window station names are case-insensitive.
    /// This window station must belong to the current session.
    /// </param>
    /// <param name="fInherit">[in] If this value
    ///            is TRUE, processes created by this process 
    /// will inherit the handle. Otherwise, 
    /// the processes do not inherit this handle. 
    /// </param>
    /// <param name="dwDesiredAccess">[in] Access to the window station</param>
    /// <returns>If the function succeeds, the return value
    ///          is the handle to the specified window station.
    /// If the function fails, the return value is NULL.</returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr OpenWindowStation(string lpszWinSta
        , bool fInherit
        , WindowStationAccessRight dwDesiredAccess
        );


    /// <summary>
    /// Assigns the specified window station to the calling process. 
    /// This enables the process to access objects in the window
    /// station such as desktops, the clipboard, and global atoms. 
    /// All subsequent operations on the window station
    /// use the access rights granted to hWinSta.
    /// </summary>
    /// <param name="hWinSta">[in] Handle to the window
    ///         station to be assigned to the calling process</param>
    /// <returns>If the function succeeds, the return value is nonzero.
    /// If the function fails, the return value is zero. </returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr SetProcessWindowStation(IntPtr hWinSta);


    /// <summary>
    /// Closes an open window station handle.
    /// </summary>
    /// <param name="hWinSta">[in] Handle
    ///         to the window station to be closed.</param>
    /// <returns>If the function succeeds, the return value is nonzero.
    /// If the function fails, the return value is zero. </returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr CloseWindowStation(IntPtr hWinSta);


    /// <summary>
    /// Opens the specified desktop object.
    /// </summary>
    /// <param name="lpszDesktop">[in] Pointer to null-terminated string 
    /// specifying the name of the desktop to be opened. 
    /// Desktop names are case-insensitive.
    /// This desktop must belong to the current window station.</param>
    /// <param name="dwFlags">[in] This parameter can
    ///          be zero or DF_ALLOWOTHERACCOUNTHOOK=0x0001</param>
    /// <param name="fInherit">[in] If this value is TRUE, processes created by 
    /// this process will inherit the handle. 
    /// Otherwise, the processes do not inherit this handle. </param>
    /// <param name="dwDesiredAccess">[in] Access
    ///         to the desktop. For a list of access rights</param>
    /// <returns>If the function succeeds, the return value is a handle to the opened desktop. 
    /// When you are finished using the handle, call the CloseDesktop function to close it.
    /// If the function fails, the return value is NULL.
    /// </returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr OpenDesktop(string lpszDesktop
        , OpenDesktopFlag dwFlags
        , bool fInherit
        , DesktopAccessRight dwDesiredAccess
        );


    /// <summary>
    /// Closes an open handle to a desktop object.
    /// </summary>
    /// <param name="hDesktop">[in] Handle to the desktop to be closed.</param>
    /// <returns>If the function succeeds, the return value is nonzero.
    /// If the function fails, the return value is zero. </returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern IntPtr CloseDesktop(IntPtr hDesktop);

    /// <summary>
    /// Assigns the specified desktop to the calling thread. 
    /// All subsequent operations on the desktop use the access rights granted to the desktop.
    /// </summary>
    /// <param name="hDesktop">[in] Handle to the desktop
    ///           to be assigned to the calling thread.</param>
    /// <returns>If the function succeeds, the return value is nonzero.
    /// If the function fails, the return value is zero. </returns>
    [DllImport("User32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    public static extern bool SetThreadDesktop(IntPtr hDesktop);
}

/// <summary>
/// REF MSDN:Window Station Security and Access Rights
/// ms-help://MS.MSDN.vAug06.en/dllproc/base/window_station_security_and_access_rights.htm
/// </summary>
[FlagsAttribute]
public enum WindowStationAccessRight : uint
{
    /// <summary>All possible access rights for the window station.</summary>
    WINSTA_ALL_ACCESS = 0x37F,

    /// <summary>Required to use the clipboard.</summary>
    WINSTA_ACCESSCLIPBOARD = 0x0004,

    /// <summary>Required to manipulate global atoms.</summary>
    WINSTA_ACCESSGLOBALATOMS = 0x0020,

    /// <summary>Required to create new desktop
    /// objects on the window station.</summary>
    WINSTA_CREATEDESKTOP = 0x0008,

    /// <summary>Required to enumerate existing desktop objects.</summary>
    WINSTA_ENUMDESKTOPS = 0x0001,

    /// <summary>Required for the window station to be enumerated.</summary>
    WINSTA_ENUMERATE = 0x0100,

    /// <summary>Required to successfully call the ExitWindows or ExitWindowsEx function. 
    /// Window stations can be shared by users and this access type can prevent other users 
    /// of a window station from logging off the window station owner.</summary>
    WINSTA_EXITWINDOWS = 0x0040,

    /// <summary>Required to read the attributes of a window station object. 
    /// This attribute includes color settings 
    /// and other global window station properties.</summary>
    WINSTA_READATTRIBUTES = 0x0002,

    /// <summary>Required to access screen contents.</summary>
    WINSTA_READSCREEN = 0x0200,

    /// <summary>Required to modify the attributes of 
    /// a window station object. 
    /// The attributes include color settings 
    /// and other global window station properties.</summary>
    WINSTA_WRITEATTRIBUTES = 0x0010,
}

/// <summary>
/// OpenDesktop 2nd param
/// </summary>
public enum OpenDesktopFlag : uint
{
    /// <summary>
    /// Default value
    /// </summary>
    DF_NONE = 0x0000,

    /// <summary>
    /// Allows processes running in other accounts on the desktop
    /// to set hooks in this process.
    /// </summary>
    DF_ALLOWOTHERACCOUNTHOOK = 0x0001,
}

/// <summary>
/// REF MSDN:Desktop Security and Access Rights
/// ms-help://MS.MSDN.vAug06.en/dllproc/base/desktop_security_and_access_rights.htm
/// </summary>
[FlagsAttribute]
public enum DesktopAccessRight : uint
{
    /// <summary>Required to create a menu on the desktop. </summary>
    DESKTOP_CREATEMENU = 0x0004,

    /// <summary>Required to create a window on the desktop. </summary>
    DESKTOP_CREATEWINDOW = 0x0002,

    /// <summary>Required for the desktop to be enumerated. </summary>
    DESKTOP_ENUMERATE = 0x0040,

    /// <summary>Required to establish any of the window hooks. </summary>
    DESKTOP_HOOKCONTROL = 0x0008,

    /// <summary>Required to perform journal playback on a desktop. </summary>
    DESKTOP_JOURNALPLAYBACK = 0x0020,

    /// <summary>Required to perform journal recording on a desktop. </summary>
    DESKTOP_JOURNALRECORD = 0x0010,

    /// <summary>Required to read objects on the desktop. </summary>
    DESKTOP_READOBJECTS = 0x0001,

    /// <summary>Required to activate the desktop
    ///          using the SwitchDesktop function. </summary>
    DESKTOP_SWITCHDESKTOP = 0x0100,

    /// <summary>Required to write objects on the desktop. </summary>
    DESKTOP_WRITEOBJECTS = 0x0080,
}

Answer 3

该服务是“无头”的，没有 UI，也没有 100% 确定（CopyFromScreen 的文档相当模糊），我预计在无头运行时会失败。在多个用户同时登录的情况下，服务如何知道要复制哪个屏幕？

另请参阅此问题

Answer 4

对于 XP/2003，Interact with Desktop 应该会有所帮助。
对于 Windows 7/Windows 2008，Interact with Desktop 的工作方式有所不同。

最适合您的解决方案是分析来自服务的登录会话，对于新会话，在用户会话中启动“桌面”进程并与该进程通信以获取屏幕。

Answer 5

这可能就像关闭浏览器中的加速器一样简单。这对我有用。在 Chrome 中，它位于系统菜单下。