.NET 窗口/屏幕录制-编程知识

.NET 窗口/屏幕录制

news/2024/11/17 3:42:21/文章来源:https://www.cnblogs.com/kybs0/p/18330811

窗口/屏幕截图适用于截图、批注等工具场景，时时获取窗口/屏幕图像数据流呢，下面讲下视频会议共享桌面、远程桌面这些场景是如何实现画面录制的。

常见的屏幕画面时时采集方案，主要有GDI、WGC、DXGI。

GDI

GDI（Graphics Device Interface）就是使用user32下WindowsAPI来实现，是 Windows 操作系统中最早、最基础的图形设备接口，满足所有windows平台。屏幕/窗口截图可以详见： .NET 窗口/屏幕截图 - 唐宋元明清2188 - 博客园 (cnblogs.com)

GDI性能不太好，尤其是针对高帧率及高分辨率需求，达到每秒20帧以上的截取,占用CPU就有点高了。另外GDI不能获取鼠标,需要在截取的图像中把鼠标画上去。

所以GDI使用很方便、不依赖GPU，对性能要求不高的截图场景建议直接使用这个方案。

WGC

Windows Graphics Capture ，是Win10引入的一种新截取屏幕以及截取窗口内容的机制 Screen capture - UWP applications | Microsoft Learn

WinRT提供接口访问，Csproj属性中添加：<UseWinRT>true</UseWinRT>

截图代码实现示例：

 1     public WgcCapture(IntPtr hWnd, CaptureType captureType)
 2     {
 3         if (!GraphicsCaptureSession.IsSupported())
 4         {
 5             throw new Exception("不支Windows Graphics Capture API");
 6         }
 7         var item = captureType == CaptureType.Screen ? CaptureUtils.CreateItemForMonitor(hWnd) : CaptureUtils.CreateItemForWindow(hWnd);
 8         CaptureSize = new Size(item.Size.Width, item.Size.Height);
 9 
10         var d3dDevice = Direct3D11Utils.CreateDevice(false);
11         _device = Direct3D11Utils.CreateSharpDxDevice(d3dDevice);
12         _framePool = Direct3D11CaptureFramePool.CreateFreeThreaded(d3dDevice, pixelFormat: DirectXPixelFormat.B8G8R8A8UIntNormalized, numberOfBuffers: 1, item.Size);
13         _desktopImageTexture = CreateTexture2D(_device, item.Size);
14         _framePool.FrameArrived += OnFrameArrived;
15         item.Closed += (i, _) =>
16         {
17             _framePool.FrameArrived -= OnFrameArrived;
18             StopCapture();
19             ItemClosed?.Invoke(this, i);
20         };
21         _session = _framePool.CreateCaptureSession(item);
22     }
23     private void OnFrameArrived(Direct3D11CaptureFramePool sender, object args)
24     {
25         try
26         {
27             using var frame = _framePool.TryGetNextFrame();
28             if (frame == null) return;
29             var data = CopyFrameToBytes(frame);
30             var captureFrame = new CaptureFrame(CaptureSize, data);
31             FrameArrived?.Invoke(this, captureFrame);
32         }
33         catch (Exception)
34         {
35             // ignored
36         }
37     }

Windows.GraphicsCapture API负责从屏幕实际抓取像素， GraphicsCaptureItem 类表示所捕获的窗口或显示， GraphicsCaptureSession 用于启动和停止捕获操作， Direct3D11CaptureFramePool 类维护要将屏幕内容复制到其中的帧的缓冲区。

WGC截图流程：

创建捕捉项：使用 CreateCaptureItemForMonitor 或 CreateCaptureItemForWindow 来创建捕捉项。
创建D3D11设备和上下文：调用 D3D11CreateDevice 创建 Direct3D 11 设备和设备上下文。这里虽然没有使用DXGI截图，但引用了DXGI的设备类型
转换为 Direct3D 设备：将 D3D11 设备转换为SharpDX Direct3D 设备对象。
创建帧池和会话：使用 Direct3D11CaptureFramePool 和 GraphicsCaptureSession。
开始捕捉：调用 StartCapture 开始会话，并注册帧到达事件。
处理帧：在帧到达事件中处理捕获的帧

我们这里是使用比较成熟的SharpDX来处理Direct3D，引用如下Nuget版本

获取到截取的D3D对象帧，帧画面转数据流：

 1     private byte[] CopyFrameToBytes(Direct3D11CaptureFrame frame)
 2     {
 3         using var bitmap = Direct3D11Utils.CreateSharpDxTexture2D(frame.Surface);
 4         _device.ImmediateContext.CopyResource(bitmap, _desktopImageTexture);
 5         // 将Texture2D资源映射到CPU内存
 6         var mappedResource = _device.ImmediateContext.MapSubresource(_desktopImageTexture, 0, MapMode.Read, MapFlags.None);
 7         //Bgra32
 8         var bytesPerPixel = 4;
 9         var width = _desktopImageTexture.Description.Width;
10         var height = _desktopImageTexture.Description.Height;
11         using var inputRgbaMat = new Mat(height, width, MatType.CV_8UC4, mappedResource.DataPointer, mappedResource.RowPitch);
12 
13         var data = new byte[CaptureSize.Width * CaptureSize.Height * bytesPerPixel];
14         if (CaptureSize.Width != width || CaptureSize.Height != height)
15         {
16             var size = new OpenCvSharp.Size(CaptureSize.Width, CaptureSize.Height);
17             Cv2.Resize(inputRgbaMat, inputRgbaMat, size, interpolation: InterpolationFlags.Linear);
18         }
19         var sourceSize = new Size(frame.ContentSize.Width, frame.ContentSize.Height);
20         if (CaptureSize == sourceSize)
21         {
22             var rowPitch = mappedResource.RowPitch;
23             for (var y = 0; y < height; y++)
24             {
25                 var srcRow = inputRgbaMat.Data + y * rowPitch;
26                 var destRowOffset = y * width * bytesPerPixel;
27                 Marshal.Copy(srcRow, data, destRowOffset, width * bytesPerPixel);
28             }
29         }
30         else
31         {
32             Marshal.Copy(inputRgbaMat.Data, data, 0, data.Length);
33         }
34 
35         _device.ImmediateContext.UnmapSubresource(_desktopImageTexture, 0);
36         return data;
37     }

将Surface对象转换为获取 SharpDX的Texture2D，映射到CPU以内存拷贝方式输出图像字节数据。

上面默认是输出三通道8位的Bgr24，如果是四通道Bgra32可以按如下从内存拷贝：

1 using var inputRgbMat = new Mat();
2 Cv2.CvtColor(inputRgbaMat, inputRgbMat, ColorConversionCodes.BGRA2BGR);
3 Marshal.Copy(inputRgbMat.Data, data, 0, data.Length);

拿到字节数据，就可以保存本地或者界面展示了。

屏幕截图Demo显示：

 1     private void CaptureButton_OnClick(object sender, RoutedEventArgs e)
 2     {
 3         var monitorHandle = MonitorUtils.GetMonitors().First().MonitorHandle;
 4         var wgcCapture = new WgcCapture(monitorHandle, CaptureType.Screen);
 5         wgcCapture.FrameArrived += WgcCapture_FrameArrived;
 6         wgcCapture.StartCapture();
 7     }
 8 
 9     private void WgcCapture_FrameArrived(object? sender, CaptureFrame e)
10     {
11         Application.Current.Dispatcher.Invoke(() =>
12         {
13             var stride = e.Size.Width * 4; // 4 bytes per pixel in BGRA format
14             var bitmap = BitmapSource.Create(e.Size.Width, e.Size.Height, 96, 96, PixelFormats.Bgra32, null, e.Data, stride);
15             bitmap.Freeze();
16             CaptureImage.Source = bitmap;
17         });
18     }

WGC利用了现代图形硬件和操作系统特性、能够提供高性能和低延迟的屏幕捕抓，适用于实时性比较高的场景如屏幕录制、视讯会议等应用。

更多的，可以参考官网屏幕捕获到视频 - UWP applications | Microsoft Learn。也可以浏览、运行我的Demo：kybs00/CaptureImageDemo (github.com)

DXGI

全名DirectX Graphics Infrastructure。从Win8开始，微软引入了一套新的接口Desktop Duplication API,而由于Desktop Duplication API是通过DXGI来提供桌面图像的，速度非常快。

DXGI使用GPU，所以cpu占用率很低，性能很高。DXGI官网文档：DXGI - Win32 apps | Microsoft Learn

因为DXGI也是使用DirectX,所以很多接口与WGC差不多。也就是通过D3D，各种QueryInterface，各种Enum，核心方法是AcquireNextFrame

它有个缺点，没办法捕获窗口内容。所以视讯会议共享窗口，是无法通过DXGI实现

我们看看Demo调用代码，

 1     private void CaptureButton_OnClick(object sender, RoutedEventArgs e)
 2     {
 3         var monitorDxgiCapture = new MonitorDxgiCapture();
 4         monitorDxgiCapture.FrameArrived += WgcCapture_FrameArrived;
 5         monitorDxgiCapture.StartCapture();
 6     }
 7 
 8     private void WgcCapture_FrameArrived(object? sender, CaptureFrame e)
 9     {
10         Application.Current?.Dispatcher.Invoke(() =>
11         {
12             var stride = e.Size.Width * 4; // 4 bytes per pixel in BGRA format
13             var bitmap = BitmapSource.Create(e.Size.Width, e.Size.Height, 96, 96, PixelFormats.Bgra32, null, e.Data, stride);
14 
15             bitmap.Freeze();
16             CaptureImage.Source = bitmap;
17         });
18     }

捕获画面帧数据：

 1     [HandleProcessCorruptedStateExceptions]
 2     private CaptureFrame CaptureFrame()
 3     {
 4         try
 5         {
 6             var data = new byte[CaptureSize.Width * CaptureSize.Height * 4];
 7             var result = _mDeskDupl.TryAcquireNextFrame(TimeOut, out _, out var desktopResource);
 8             if (result.Failure) return null;
 9 
10             using var tempTexture = desktopResource?.QueryInterface<Texture2D>();
11             _mDevice.ImmediateContext.CopyResource(tempTexture, _desktopImageTexture); //拷贝图像纹理：GPU硬件加速的纹理复制
12             desktopResource?.Dispose();
13 
14             var desktopSource = _mDevice.ImmediateContext.MapSubresource(_desktopImageTexture, 0, MapMode.Read, MapFlags.None);
15             using var inputRgbaMat = new Mat(_screenSize.Height, _screenSize.Width, MatType.CV_8UC4, desktopSource.DataPointer);
16             if (CaptureSize.Width != _screenSize.Width || CaptureSize.Height != _screenSize.Height)
17             {
18                 var size = new OpenCvSharp.Size(CaptureSize.Width, CaptureSize.Height);
19                 Cv2.Resize(inputRgbaMat, inputRgbaMat, size, interpolation: InterpolationFlags.Linear);
20             }
21             Marshal.Copy(inputRgbaMat.Data, data, 0, data.Length);
22 
23             var captureFrame = new CaptureFrame(CaptureSize, data);
24             _mDevice.ImmediateContext.UnmapSubresource(_desktopImageTexture, 0);
25             //释放帧
26             _mDeskDupl.ReleaseFrame();
27             return captureFrame;
28         }
29         catch (AccessViolationException)
30         {
31             return null;
32         }
33         catch (Exception)
34         {
35             return null;
36         }
37     }