C# 根据窗口句柄获取窗口截图

C# 根据窗口句柄获取窗口截图

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C# 根据窗口句柄获取窗口截图

作者：唐宋元明清的博客

原文链接： https://www.cnblogs.com/kybs0/p/15768990.html

本章介绍如何通过句柄，截取指定窗口内容，以及截取失败的场景。

一、根据窗口句柄获取窗口截图

先创建一个测试窗口程序A，显示如下：

同时我们把此窗口的句柄显示到一个文本输入框内。

TestBox.Text = new WindowInteropHelper(this).Handle.ToString();

如上图所示，1774674是此窗口的句柄值。
然后，我们新建一个窗口程序B，对窗口A进行截图并展示。

var windowIntPtr = new IntPtr(1774674);
var bitmapImage = GetWindowShotCut(windowIntPtr);
TestImage.Source = bitmapImage;

截图方法及详细操作如下：

private BitmapImage GetWindowShotCut(IntPtr intPtr)
{var image = WindowCaptureHelper.GetShotCutImage(intPtr);var bitmapImage = BitmapConveters.ConvertToBitmapImage(image);return bitmapImage;
}

WindowCaptureHelper代码如下：

public class WindowCaptureHelper{[DllImport("user32.dll")]private static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rectangle rect);[DllImport("gdi32.dll")]private static extern IntPtr CreateCompatibleDC(IntPtr hdc);[DllImport("gdi32.dll")]private static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);[DllImport("gdi32.dll")]private static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);[DllImport("gdi32.dll")]private static extern int DeleteDC(IntPtr hdc);[DllImport("user32.dll")]private static extern bool PrintWindow(IntPtr hwnd, IntPtr hdcBlt, int nFlags);[DllImport("user32.dll")]private static extern IntPtr GetWindowDC(IntPtr hwnd);public static Bitmap GetShotCutImage(IntPtr hWnd){var hscrdc = GetWindowDC(hWnd);var windowRect = new Rectangle();GetWindowRect(hWnd, ref windowRect);int width = Math.Abs(windowRect.Width- windowRect.X);int height = Math.Abs(windowRect.Height- windowRect.Y);var hbitmap = CreateCompatibleBitmap(hscrdc, width, height);var hmemdc = CreateCompatibleDC(hscrdc);SelectObject(hmemdc, hbitmap);PrintWindow(hWnd, hmemdc, 0);var bmp = Image.FromHbitmap(hbitmap);DeleteDC(hscrdc);DeleteDC(hmemdc);return bmp;}}

BitmapConveters：代码如下：

public class BitmapConveters{[DllImport("gdi32")]static extern int DeleteObject(IntPtr o);public static BitmapSource ConvertToBitMapSource(Bitmap bitmap){IntPtr intPtrl = bitmap.GetHbitmap();BitmapSource bitmapSource = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(intPtrl,IntPtr.Zero,Int32Rect.Empty,BitmapSizeOptions.FromEmptyOptions());DeleteObject(intPtrl);return bitmapSource;}public static BitmapImage ConvertToBitmapImage(Bitmap bitmap){using (MemoryStream stream = new MemoryStream()){bitmap.Save(stream, ImageFormat.Bmp);stream.Position = 0;BitmapImage result = new BitmapImage();result.BeginInit();result.CacheOption = BitmapCacheOption.OnLoad;result.StreamSource = stream;result.EndInit();result.Freeze();return result;}}}

截图后显示如下：

二、窗口截图失败

窗口A在特定场景下，我们截到的窗口内容是黑色的：

截图获取失败了，窗口A做了什么处理？

定位发现是属性AllowsTransparency="True"的锅，搜索了下，网上也有同样的反馈：

Taking a screenshot of windows with AllowsTransparency="True" (microsoft.com)^[1]

c# - Capture transparent WPF Window for streaming - Stack Overflow^[2]

.net - Transparent child window renders as black when screen sharing main window on Microsoft Teams - Stack Overflow^[3]

有个Issue在跟进： Screen capture semi-transparent windows? · Issue #334 · microsoft/WindowsCompositionSamples (github.com)^[4]

官方大佬说，这是他们的一个BUG。在win10 2004更新版本中，已处理。

不过，我现在是win11，依然还有问题。。。我是在win10上直接更新到win11，可能原来那个win10企业LTSC版本有点老，win11更新只更新了UI？或者win11是基于原来旧分支开发的？等回复中...
Taking a screenshot of windows with AllowsTransparency="True" · Issue #358 · microsoft/WindowsCompositionSamples (github.com)^[5]

github^[6]

参考资料

[1]

Taking a screenshot of windows with AllowsTransparency=True: https://social.msdn.microsoft.com/Forums/office/en-US/3368f8f5-efb3-40cc-add5-f5311a74a954/taking-a-screenshot-of-windows-with-allowstransparencytrue

[2]

c# - Capture transparent WPF Window for streaming - Stack Overflow: https://stackoverflow.com/questions/50888023/capture-transparent-wpf-window-for-streaming

[3]

.net - Transparent child window renders as black when screen sharing main window on Microsoft Teams - Stack Overflow: https://stackoverflow.com/questions/65514472/transparent-child-window-renders-as-black-when-screen-sharing-main-window-on-mic

[4]

Screen capture semi-transparent windows? · Issue #334 · microsoft/WindowsCompositionSamples (github.com Screen capture semi-transparent windows? · Issue #334: https://github.com/microsoft/WindowsCompositionSamples/issues/334

[5]

Taking a screenshot of windows with AllowsTransparency=True · Issue #358 ·: https://github.com/microsoft/WindowsCompositionSamples/issues/358

[6]

github: https://github.com/Kybs0

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