打印 Panel 内容的图像，不包括任何外部重叠 Window

Question

我有一些问题。
我在表单中有一个面板和一个图片框。
我想打开一个 Windows 应用程序（例如记事本）并将其添加到面板。
然后我想在 PictureBox 中显示面板内容的图像：

我的代码：

[DllImport("user32.dll", SetLastError = true)]
private static extern long SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

[DllImport("user32.dll", SetLastError = true)]
private static extern long SetWindowPos(IntPtr hwnd, long hWndInsertAfter, long x, long y, long cx, long cy, long wFlags);

[DllImport("user32.dll", SetLastError = true)]
private static extern bool MoveWindow(IntPtr hwnd, int x, int y, int cx, int cy, bool repaint);

IntPtr appWin1;

private void Notepad_Button_Click(object sender, EventArgs e)
{
    ProcessStartInfo ps1 = new ProcessStartInfo(@"notepad.exe");
    ps1.WindowStyle = ProcessWindowStyle.Minimized;
    Process p1 = Process.Start(ps1);
    System.Threading.Thread.Sleep(5000); // Allow the process to open it's window
    appWin1 = p1.MainWindowHandle;
    // Put it into this form
    SetParent(appWin1, this.panel1.Handle);
}


private void timer1_Tick(object sender, EventArgs e)
{
    Bitmap bm = new Bitmap(panel1.Width, panel1.Height);
    Graphics g = Graphics.FromImage(bm);
    g.CopyFromScreen(0, 0, 0, 0, bm.Size);
    pictureBox1.Image = bm;
    
}

private void Form5_Load(object sender, EventArgs e)
{

}

private void panel1_Paint(object sender, PaintEventArgs e)
{

}

private void timer2_Tick(object sender, EventArgs e)
{
    MoveWindow(appWin1, 0, 0, this.panel1.Width, this.panel1.Height, true);
}

private void pictureBox1_Click(object sender, EventArgs e)
{

}

运行这段代码：

问题是这样的：我只想获取面板内部的内容，但是在我的面板前面移动的任何其他 Window 都包含在 PictureBox 中显示的位图中：

[}3

如图所示，外部页面放在panel1时，也会出现在pictureBox1（图中红框）
我只希望记事本出现在 pictureBox1 中，无论 Window 悬停在 panel1.

上

Answer 1

由于您想将 Panel 的内容呈现为 Bitmap - 它正在托管外部应用程序 - 您不能使用 Control.DrawToBitmap()：托管应用程序的内容，父级调用 SetParent()，赢得' 被打印出来。
由于您还想从渲染中排除可能悬停在面板上的任何其他 Window，您可以使用 PrintWindow 函数，传递面板的父窗体的句柄。
表单将收到 WM_PRINT 或 WM_PRINTCLIENT 消息，并将自身打印到指定的设备上下文：在本例中，从位图生成。

这不是屏幕截图：Window 将自身及其内容绘制到 DC，因此其他 Windows 是否悬停/部分完全重叠并不重要，结果是一样的。

我正在使用 DwmGetWindowAttribute，设置 DWMWA_EXTENDED_FRAME_BOUNDS，以获得要打印的 Window 的边界。它可能看起来冗余，但是，如果您的应用不是 DpiAware 并且您有一个高 Dpi 屏幕，那么在这种情况下它会显得不那么冗余 .最好有它，IMO。
此功能比 GetWindowRect 或 GetClientRect 更可靠，它将 return 在可变 DPI 上下文中纠正措施。

您不能将子 Window 的句柄传递给此函数，所以我使用父窗体的句柄生成位图，然后 select 面板所在的部分位于。这取决于：

[ParentForm].RectangleToClient([Child].RectangleToScreen([Child].ClientRectangle))

启动进程和父记事本的Window到面板控件：

private void Notepad_Button_Click(object sender, EventArgs e)
{
    var psi = new ProcessStartInfo(@"notepad.exe") { WindowStyle = ProcessWindowStyle.Minimized };
    using (var p = Process.Start(psi)) {
        p.WaitForInputIdle();
        var handle = p.MainWindowHandle;
        if (handle != IntPtr.Zero) {
            SetParent(handle, panel1.Handle);
            MoveWindow(handle, 0, 0, panel1.Width, panel1.Height, true);
        }
    }
}

现在，只要您想将面板所在的表单部分呈现为位图，请调用 RenderWindow 并获取您感兴趣的部分：面板的 ClientRectangle。

using (var image = RenderWindow(this.Handle, true, false)) {
    if (image is null) return;
    if (WindowState == FormWindowState.Minimized) return;
    var panelRect = RectangleToClient(panel1.RectangleToScreen(panel1.ClientRectangle));
    pictureBox1.Image?.Dispose();
    pictureBox1.Image = image.Clone(panelRect, PixelFormat.Format32bppArgb);
}

// [...]

public static Bitmap RenderWindow(IntPtr hWnd, bool clientAreaOnly, bool tryGetFullContent = false)
{
    var printOption = clientAreaOnly ? PrintWindowOptions.PW_CLIENTONLY : PrintWindowOptions.PW_DEFAULT;
    printOption = tryGetFullContent ? PrintWindowOptions.PW_RENDERFULLCONTENT : printOption;
    var hResult = DwmGetWindowAttribute(hWnd, DWMWINDOWATTRIBUTE.DWMWA_EXTENDED_FRAME_BOUNDS, out Rectangle dwmRect, Marshal.SizeOf<Rectangle>());
    if (hResult < 0) {
        Marshal.ThrowExceptionForHR(hResult);
        return null;
    }

    if (dwmRect.Width <= 0 || dwmRect.Height <= 0) return null;

    var bmp = new Bitmap(dwmRect.Width, dwmRect.Height);
    using (var g = Graphics.FromImage(bmp)) {
        var hDC = g.GetHdc();
        try {
            var success = PrintWindow(hWnd, hDC, printOption);
            if (!success) {
                // Failed, see what happened
                var win32Error = Marshal.GetLastWin32Error();
                return null;
            }
            return bmp;
        }
        finally {
            g.ReleaseHdc(hDC);
        }
    }
}

Win32 声明:

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

[DllImport("user32.dll", SetLastError = true)]
static extern bool MoveWindow(IntPtr hWnd, int x, int y, int nWidth, int nHeight, bool bRepaint);

public enum PrintWindowOptions : uint
{
    PW_DEFAULT = 0,
    PW_CLIENTONLY = 1,
    PW_RENDERFULLCONTENT = 2  // Undocumented. Use, e.g., with a WebBrowser
}

[DllImport("user32.dll", SetLastError = true)]
static extern internal bool PrintWindow(IntPtr hwnd, IntPtr hDC, PrintWindowOptions nFlags);

public enum DWMWINDOWATTRIBUTE : uint
{
    DWMWA_NCRENDERING_ENABLED = 1,      // [get] Is non-client rendering enabled/disabled
    DWMWA_NCRENDERING_POLICY,           // [set] DWMNCRENDERINGPOLICY - Non-client rendering policy - Enable or disable non-client rendering
    DWMWA_TRANSITIONS_FORCEDISABLED,    // [set] Potentially enable/forcibly disable transitions
    DWMWA_ALLOW_NCPAINT,                // [set] Allow contents rendered In the non-client area To be visible On the DWM-drawn frame.
    DWMWA_CAPTION_BUTTON_BOUNDS,        // [get] Bounds Of the caption button area In window-relative space.
    DWMWA_NONCLIENT_RTL_LAYOUT,         // [set] Is non-client content RTL mirrored
    DWMWA_FORCE_ICONIC_REPRESENTATION,  // [set] Force this window To display iconic thumbnails.
    DWMWA_FLIP3D_POLICY,                // [set] Designates how Flip3D will treat the window.
    DWMWA_EXTENDED_FRAME_BOUNDS,        // [get] Gets the extended frame bounds rectangle In screen space
    DWMWA_HAS_ICONIC_BITMAP,            // [set] Indicates an available bitmap When there Is no better thumbnail representation.
    DWMWA_DISALLOW_PEEK,                // [set] Don't invoke Peek on the window.
    DWMWA_EXCLUDED_FROM_PEEK,           // [set] LivePreview exclusion information
    DWMWA_CLOAK,                        // [set] Cloak Or uncloak the window
    DWMWA_CLOAKED,                      // [get] Gets the cloaked state Of the window. Returns a DWMCLOACKEDREASON object
    DWMWA_FREEZE_REPRESENTATION,        // [set] BOOL, Force this window To freeze the thumbnail without live update
    PlaceHolder1,
    PlaceHolder2,
    PlaceHolder3,
    DWMWA_ACCENTPOLICY = 19
}

[DllImport("dwmapi.dll", SetLastError = true)]
static extern internal int DwmGetWindowAttribute(IntPtr hwnd, DWMWINDOWATTRIBUTE dwAttribute, out Rectangle pvAttribute, int cbAttribute);

打印 Panel 内容的图像，不包括任何外部重叠 Window

Print an image of the content of a Panel excluding any external overlapping Window

c#

winforms

bitmap

panel

picturebox