C#利用avicap32.dll实现摄像头抓拍与录像

林舟

发布时间：2026-10-13 | 1人浏览过

原创

本文分享了在C#开发中如何利用系统API控制摄像头进行实时监控、图像采集及录像的技术方案。通过使用未托管代码方式加载 avicap32.dll，可以实现无需第三方组件的本地化视频处理。

核心实现原理

C#本身不直接支持VFW（Video for Windows）旧版协议，但可以通过P/Invoke技术导入Windows系统中的 avicap32.dll 动态链接库来完成硬件交互。该库提供了捕获窗口的创建、消息发送及媒体流控制能力。

关键常量定义

操作摄像头依赖大量的WPARAM和LPARAM消息参数。我们需要将标准Windows消息与VFW特有的 WM_CAP_START 系列命令进行组合映射。

// 基础窗口消息
private const int WM_USER = 0x400;
private const int WS_CHILD = 0x40000000;
private const int WS_VISIBLE = 0x10000000;

// VFW 视频捕获起始消息码
private const int WM_CAP_START = WM_USER;

// 具体的控制指令
private const int WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10; // 连接指定索引的摄像头
private const int WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11; // 断开连接
private const int WM_CAP_SAVEDIB = WM_CAP_START + 25; // 保存单帧为DIB/BMP
private const int WM_CAP_GRAB_FRAME = WM_CAP_START + 60; // 抓取一帧到内存
private const int WM_CAP_SEQUENCE = WM_CAP_START + 62; // 开始连续录制序列
private const int WM_CAP_FILE_SET_CAPTURE_FILEA = WM_CAP_START + 20; // 设置录像保存路径
private const int WM_CAP_SET_PREVIEW = WM_CAP_START + 50; // 开启预览模式
private const int WM_CAP_SET_SCALE = WM_CAP_START + 53; // 缩放视频流

完整控制类实现

为了便于集成，我们将上述逻辑封装在一个名为 Pick 的类中。该类管理着摄像头句柄状态，并暴露了简单的启动、停止、抓图和录像接口。

using System;
using System.Runtime.InteropServices;

public class Pick
{
    private const int WM_USER = 0x400;
    private const int WS_CHILD = 0x40000000;
    private const int WS_VISIBLE = 0x10000000;
    private const int WM_CAP_START = WM_USER;
    
    // ... (此处省略部分中间常量，参考上文定义) ...
    private const int WM_CAP_SAVEDIB = WM_CAP_START + 25;
    private const int WM_CAP_SEQUENCE = WM_CAP_START + 62;
    private const int WM_CAP_FILE_SET_CAPTURE_FILEA = WM_CAP_START + 20;
    private const int WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10;
    private const int WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11;
    private const int WM_CAP_STOP = WM_CAP_START + 68;
    private const int WM_CAP_SET_OVERLAY = WM_CAP_START + 51;
    private const int WM_CAP_SET_PREVIEW = WM_CAP_START + 50;
    private const int WM_CAP_SET_CALLBACK_VIDEOSTREAM = WM_CAP_START + 6;
    private const int WM_CAP_SET_CALLBACK_ERROR = WM_CAP_START + 2;
    private const int WM_CAP_SET_CALLBACK_STATUSA = WM_CAP_START + 3;
    private const int WM_CAP_SET_SCALE = WM_CAP_START + 53;
    private const int WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52;

    private IntPtr hWndC;
    private bool bStat = false;
    private IntPtr mControlPtr;
    private int mWidth;
    private int mHeight;
    private int mLeft;
    private int mTop;

    /// <summary>
    /// 初始化摄像头参数
    /// </summary>
    public Pick(IntPtr handle, int left, int top, int width, int height)
    {
        mControlPtr = handle;
        mWidth = width;
        mHeight = height;
        mLeft = left;
        mTop = top;
    }

    [DllImport("avicap32.dll")]
    private static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID);

    [DllImport("User32.dll")]
    private static extern bool SendMessage(IntPtr hWnd, int wMsg, int wParam, long lParam);

    /// <summary>
    /// 开始显示图像预览
    /// </summary>
    public void Start()
    {
        if (bStat) return;
        bStat = true;
        
        byte[] lpszName = new byte[100];
        // 创建捕获窗口
        hWndC = capCreateCaptureWindowA(lpszName, WS_CHILD | WS_VISIBLE, mLeft, mTop, mWidth, mHeight, mControlPtr, 0);
        
        if (hWndC.ToInt32() != 0)
        {
            // 配置回调函数与显示属性
            SendMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, 0, 0);
            SendMessage(hWndC, WM_CAP_SET_CALLBACK_ERROR, 0, 0);
            SendMessage(hWndC, WM_CAP_SET_CALLBACK_STATUSA, 0, 0);
            SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, 0, 0); // 默认连接设备0
            SendMessage(hWndC, WM_CAP_SET_SCALE, 1, 0);
            SendMessage(hWndC, WM_CAP_SET_PREVIEWRATE, 66, 0);
            SendMessage(hWndC, WM_CAP_SET_OVERLAY, 1, 0);
            SendMessage(hWndC, WM_CAP_SET_PREVIEW, 1, 0);
        }
    }

    /// <summary>
    /// 停止显示
    /// </summary>
    public void Stop()
    {
        SendMessage(hWndC, WM_CAP_DRIVER_DISCONNECT, 0, 0);
        bStat = false;
    }

    /// <summary>
    /// 抓图保存为.bmp
    /// </summary>
    public void GrabImage(string path)
    {
        IntPtr hBmp = Marshal.StringToHGlobalAnsi(path);
        SendMessage(hWndC, WM_CAP_SAVEDIB, 0, hBmp.ToInt64());
    }

    /// <summary>
    /// 开始录制AVI视频
    /// </summary>
    public void Kinescope(string path)
    {
        IntPtr hFilePtr = Marshal.StringToHGlobalAnsi(path);
        SendMessage(hWndC, WM_CAP_FILE_SET_CAPTURE_FILEA, 0, hFilePtr.ToInt64());
        SendMessage(hWndC, WM_CAP_SEQUENCE, 0, 0);
    }

    /// <summary>
    /// 停止录像
    /// </summary>
    public void StopKinescope()
    {
        SendMessage(hWndC, WM_CAP_STOP, 0, 0);
    }
}

使用示例与注意事项

在实际WinForms项目中，你可以实例化该类并将摄像头画面嵌入到 Panel 或 UserControl 中：

获取句柄：从作为容器的控件获取 IntPtr Handle。
初始化：var picker = new Pick(panel1.Handle, 0, 0, panel1.Width, panel1.Height);
启动预览：调用 picker.Start();
执行操作：根据业务需求调用 GrabImage() 或 Kinescope()。
清理资源：在使用结束时，务必调用 picker.Stop(); 以释放摄像头独占权限，否则其他程序将无法访问该摄像头。