近日心血来潮，研究了下控制摄像头，老实说原理很简单，想深入又是那么的难。话不多说上代码，再留下点疑问，就是这么把视频的流文件截取下来。

using System.Runtime.InteropServices;
using System.Drawing.Imaging;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace mycamera
{
    public partial class Form1 : Form
    {
        //定义常量
        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;
        private const int WM_CAP_STOP = WM_CAP_START + 68;
        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_SAVEDIB = WM_CAP_START + 25;
        private const int WM_CAP_GRAB_FRAME = WM_CAP_START + 60;
        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_SEQUENCE_NOFILE = WM_CAP_START + 63;
        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_CALLBACK_FRAME = WM_CAP_START + 5;
        private const int WM_CAP_SET_SCALE = WM_CAP_START + 53;
        private const int WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52;
        private int hHwnd;
        private const int port = 2000;
        public Form1()
        {
            InitializeComponent();
        }
        public struct videohdr_tag
        {
            public byte[] lpData;
            public int dwBufferLength;
            public int dwBytesUsed;
            public int dwTimeCaptured;
            public int dwUser;
            public int dwFlags;
            public int[] dwReserved;

        }
        public delegate bool CallBack(int hwnd, int lParam);
        //引用API AVICAP32调用摄像头
        [DllImport("avicap32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        public static extern int capCreateCaptureWindowA([MarshalAs(UnmanagedType.VBByRefStr)]   ref   string lpszWindowName, int dwStyle, int x, int y, int nWidth, short nHeight, int hWndParent, int nID);
        [DllImport("avicap32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        public static extern bool capGetDriverDescriptionA(short wDriver, [MarshalAs(UnmanagedType.VBByRefStr)]   ref   string lpszName, int cbName, [MarshalAs(UnmanagedType.VBByRefStr)]   ref   string lpszVer, int cbVer);
        [DllImport("user32", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        public static extern bool DestroyWindow(int hndw);
        //定义向窗体发送数据方法
        [DllImport("user32", EntryPoint = "SendMessageA", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        public static extern int SendMessage(int hwnd, int wMsg, int wParam, [MarshalAs(UnmanagedType.AsAny)]   object lParam);

        [DllImport("user32", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        public static extern int SetWindowPos(int hwnd, int hWndInsertAfter, int x, int y, int cx, int cy, int wFlags);
        [DllImport("vfw32.dll")]
        public static extern string capVideoStreamCallback(int hwnd, videohdr_tag videohdr_tag);
        [DllImport("vicap32.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
        public static extern bool capSetCallbackOnFrame(int hwnd, string s);

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenCapture();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            closecapture();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            cutimg();
        }

        private void button4_Click(object sender, EventArgs e)
        {

        }
        private void button5_Click(object sender, EventArgs e)
        {
            cutavi();
        }
        private void button6_Click(object sender, EventArgs e)
        {
            stopavi();
        }
        //定义打开摄像头函数
        private void OpenCapture()
        {
            //定义视频窗口的长宽
            int intWidth = this.panel1.Width;
            int intHeight = this.panel1.Height;
            int intDevice = 0;
            string refDevice = intDevice.ToString();
            //创建视频窗口并得到句柄
            hHwnd = Form1.capCreateCaptureWindowA(ref   refDevice, 1342177280, 0, 0, 640, 480, this.panel1.Handle.ToInt32(), 0);
            if (Form1.SendMessage(hHwnd, 0x40a, intDevice, 0) > 0)
            {
                Form1.SendMessage(this.hHwnd, 0x435, -1, 0);
                Form1.SendMessage(this.hHwnd, 0x434, 0x42, 0);
                Form1.SendMessage(this.hHwnd, 0x432, -1, 0);
                Form1.SetWindowPos(this.hHwnd, 1, 0, 0, intWidth, intHeight, 6);
            }
            else
            {
                Form1.DestroyWindow(this.hHwnd);
            }
        }
        //定义关闭摄像头
        private void closecapture()
        {
            Form1.SendMessage(this.hHwnd, 0x40b, 0, 0);
            Form1.DestroyWindow(this.hHwnd);
        }
        //截图函数
        private void cutimg()
        {

            try
            {

                Form1.SendMessage(this.hHwnd, 0x41e, 0, 0);
                //从当前剪切板获取数据
                IDataObject obj1 = Clipboard.GetDataObject();
                //判断数据是否为BITMAP
                if (obj1.GetDataPresent(typeof(Bitmap)))
                {
                    //保存图像
                    Image image1 = (Image)obj1.GetData(typeof(Bitmap));
                    //实例化一个保存控件
                    SaveFileDialog SaveFileDialog1 = new SaveFileDialog();
                    SaveFileDialog1.FileName = DateTime.Now.ToString("yyyyMMddhhmmss");
                    SaveFileDialog1.Filter = "Image Files(*.JPG;*.GIF)|*.JPG;*.GIF|All files (*.*)|*.*";
                    if (SaveFileDialog1.ShowDialog() == DialogResult.OK)
                    {
                        image1.Save(SaveFileDialog1.FileName, ImageFormat.Bmp);
                    }
                }
            }
            catch
            {
            }

        }
        //录像函数
        private void cutavi()
        {
            string path;
            SaveFileDialog SaveFileDialog2 = new SaveFileDialog();
            SaveFileDialog2.FileName = DateTime.Now.ToString("yyyyMMddhhmmss");
            SaveFileDialog2.Filter = "AVI Files(*.avi)|*.avi|All files (*.*)|*.*";
            if (SaveFileDialog2.ShowDialog() == DialogResult.OK)
            {
                path = SaveFileDialog2.FileName;
            }
            else
            {
                return;
            }
            IntPtr hBmp = Marshal.StringToHGlobalAnsi(path);
            SendMessage(this.hHwnd, WM_CAP_FILE_SET_CAPTURE_FILEA, 0, hBmp.ToInt64());
            SendMessage(this.hHwnd, WM_CAP_SEQUENCE, 0, 0);
        }
        //停止录像函数
        private void stopavi()
        {
            SendMessage(this.hHwnd, WM_CAP_STOP, 0, 0);

        }