Question

我正在尝试在C＃.net中创建一个应用程序，它捕获当前活动窗口的屏幕截图，包括必须使用滚动条滚动的区域。我找到了以下代码来截取屏幕截图。为了清楚起见，我希望代码能够获取活动窗口的屏幕截图，包括未显示的区域，并且只能使用滚动条显示。

public class ScreenShot
{
    /// <summary>
    /// Captures the screenshot of the entire desktop
    /// </summary>
    /// <returns>Image object containing the screenshot of the desktop</returns>
    private Image CaptureDesktop()
    {
        return CaptureWindow(User32.GetDesktopWindow());
    }

    public Image CaptureAciveWindow()
    {
        return CaptureWindow(User32.GetForegroundWindow());
    }

    /// <summary>
    /// An Internal method, that captures the screenshot of any given Application window, given its Handle.
    /// </summary>
    /// <param name="handle">The handle of the window you want to Capture</param>
    /// <returns>An Image object containing the screenshot of the active application window</returns>
    private Image CaptureWindow(IntPtr handle)
    {
        // get te hDC of the target window
        IntPtr hdcSrc = User32.GetWindowDC(handle);
        // get the size
        User32.RECT windowRect = new User32.RECT();
        User32.GetWindowRect(handle, ref windowRect);
        int width = windowRect.right - windowRect.left;
        int height = windowRect.bottom - windowRect.top;
        // create a device context we can copy to
        IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
        // create a bitmap we can copy it to,
        // using GetDeviceCaps to get the width/height
        IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
        // select the bitmap object
        IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
        // bitblt over
        GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);
        // restore selection
        GDI32.SelectObject(hdcDest, hOld);
        // clean up 
        GDI32.DeleteDC(hdcDest);
        User32.ReleaseDC(handle, hdcSrc);
        // get a .NET image object for it
        Image img = Image.FromHbitmap(hBitmap);
        // free up the Bitmap object
        GDI32.DeleteObject(hBitmap);

        return img;
    }

    /// <summary>
    /// Helper class containing Gdi32 API functions
    /// </summary>
    private class GDI32
    {
        public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter

        [DllImport("gdi32.dll")]
        public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
            int nWidth, int nHeight, IntPtr hObjectSource,
            int nXSrc, int nYSrc, int dwRop);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
            int nHeight);
        [DllImport("gdi32.dll")]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteDC(IntPtr hDC);
        [DllImport("gdi32.dll")]
        public static extern bool DeleteObject(IntPtr hObject);
        [DllImport("gdi32.dll")]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
    }

    /// <summary>
    /// Helper class containing User32 API functions
    /// </summary>
    private class User32
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }

        [DllImport("user32.dll")]
        public static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowDC(IntPtr hWnd);
        [DllImport("user32.dll")]
        public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
        /// <summary>
        /// Gets the Handle for current active window
        /// </summary>
        /// <returns>Active windows Handle</returns>
        [DllImport("user32.dll")]
        public static extern IntPtr GetForegroundWindow();
    }
}

Answer 1

你在这里做出一个假设并不一定是真的：那里有一些已经在未展开区域等待的东西。应用程序可以为某个高度或宽度构建滚动条，并且实际上不会向表面渲染任何内容，直到用户实际拖动滚动条。您要捕获的图像仅存在于潜在的图像中。这可用于提高性能 - 考虑即时加载或减少内存使用。这是一种相当常见的技术，所以你所要求的并没有多大意义。

Answer 2

在不使用任何Win32 API调用的情况下捕获屏幕内容，只需在CodeProject使用.NET 2.0。

Answer 3

如果您尝试获取屏幕外的内容，则WM_PRINT 可能有效。 BitBlt肯定不会。

见：

Answer 4

您需要将整个窗口/表单重绘到图形对象上。可以在this CodeProject article中找到如何完成此操作的（简单）示例。您需要实现对项目中所需的所有控件的支持。此外，如果您在示例应用程序中调整窗口大小（隐藏一些控件）并进行测试打印，您将看到主窗体（它只是另一个控件）被绘制在其他控件上，这不是真正的问题但是看起来不太好 - 如果这是一个问题，你可以删除绘制主表单的支持。

或者，如果使用或切换到WPF，您可以使用PrintDialog.PrintVisual（）打印控件（包括主窗口）。

如何在C＃中截取全尺寸窗口的屏幕截图

4 个答案: