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C#调用USB摄像头总是跳出选择摄像头 RRS feed

  • 问题

  • RT::调用本地摄像头会出现一个对话框,让我选择使用哪个摄像头,选择完毕后,进入程序调试时无法显示。
    以下是我调用摄像头的类(用了AVIcap),想用Directshow来做,但完全不会。。。。

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Runtime.InteropServices;
    
    namespace ZYPLAT.PLACE
    {
        public class Camera
        {
            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 IntPtr hWndC;
            private IntPtr mControlPtr;
            private bool bWorkStart = false;
            private int mWidth;
            private int mHeight;
            private int mLeft;
            private int mTop;
    
            /// <summary>
            /// 初始化显示图像
            /// </summary>
            /// <param name="handle">控件的句柄 </param>
            /// <param name="left">开始显示的左边距 </param>
            /// <param name="top">开始显示的上边距 </param>
            /// <param name="width">要显示的宽度 </param>
            /// <param name="height">要显示的长度 </param>
            public Camera(IntPtr handle, int left, int top, int width, int height)  
            {
                mControlPtr = handle;
                mWidth = width;
                mHeight = height;
                mLeft = left;
                mTop = top;
            }
            // 创建捕捉窗口
            //HWND VFWAPI capCreateCaptureWindow(
            //      LPCSTR lpszWindowName,// 捕捉窗口名字
            //      DWORD dwStyle,// 捕捉窗口的风格
            //      int x,// 窗口左上角x轴坐标
            //      int y,// 窗口左上角y轴坐标
            //      int nWidth,// 窗口的宽度
            //      int nHeight,// 窗口的高度
            //      HWND HWnd,// 父窗口句柄
            //      Int nID// 捕捉窗口的ID号
            //);
            //如果该函数调用成功 则函数返回窗口的句柄 否则函数返回NULL。
            [DllImport("avicap32.dll")]
            private static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID);
    
        //      视频格式设置对话框
        //    BOOL capDlgVideoFormat( hwnd ); // hwnd:捕捉窗口句柄
        //视频格式设置对话框对于每一个捕捉驱动程序来说,是唯一的。而且,有些驱动程序不一定支持这一功能。应用程序可以通过检测CAPDRIVERCAPS结构的成员变量fHasDlgVideoFormat来判断驱动程序是否支持这一功能。
    
            [DllImport("avicap32.dll")]
            private static extern int capGetVideoFormat(IntPtr hWnd, IntPtr psVideoFormat, int wSize);
            [DllImport("User32.dll")]
            private static extern bool SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);
    
            /// <summary>
            /// 开始显示图像
            /// </summary>
            public void Start()
            {
                if (bWorkStart)
                {
                    return;
                }
                bWorkStart = true;
                byte[] lpszName = new byte[100];
                hWndC = capCreateCaptureWindowA(lpszName, WS_CHILD | WS_VISIBLE, mLeft, mTop, mWidth, mHeight, mControlPtr, 0);
                if (hWndC.ToInt32() != 0)
                {
                    SendMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, IntPtr.Zero, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_SET_CALLBACK_ERROR, IntPtr.Zero, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_SET_CALLBACK_STATUSA, IntPtr.Zero, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, IntPtr.Zero, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_SET_SCALE, (IntPtr)1, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_SET_PREVIEWRATE, (IntPtr)66, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_SET_OVERLAY, (IntPtr)1, IntPtr.Zero);
                    SendMessage(hWndC, WM_CAP_SET_PREVIEW, (IntPtr)1, IntPtr.Zero);
                }
                return;
            }
    
            /// <summary>
            /// 停止显示图像
            /// </summary>
            public void Stop()
            {
                SendMessage(hWndC, WM_CAP_DRIVER_DISCONNECT, IntPtr.Zero, IntPtr.Zero);
                bWorkStart = false;
            }
    
            /// <summary>
            /// 抓图
            /// </summary>
            /// <param name="path">要保存bmp文件的路径 </param>
            public void GrabImage(string path)
            {
                IntPtr hBmp = Marshal.StringToHGlobalAnsi(path);  //将System.String内容复制到非托管内存当中
                SendMessage(hWndC, WM_CAP_SAVEDIB, IntPtr.Zero, hBmp);
            }
    
            ///<summary>
            ///录像
            ///</summary>
            ///<param name="path">要保存avi文件的路径</param>
            public void Kinescope(string path)
            {
                IntPtr hCap = Marshal.StringToHGlobalAnsi(path);
                SendMessage(hWndC, WM_CAP_FILE_SET_CAPTURE_FILEA, IntPtr.Zero, hCap);
                SendMessage(hWndC, WM_CAP_SEQUENCE, IntPtr.Zero, hCap);
            }
    
            ///<summary>
            ///停止录像
            ///</summary>
            public void StopKinescope()
            {
                SendMessage(hWndC, WM_CAP_STOP, IntPtr.Zero, IntPtr.Zero);
            }
        }
    }
    

    以上这个类我只用了抓图,我只想做个抓图的,第一次调试可以使用摄像头的,第二次就不行,需要拔插USB摄像头才可以再次调试使用。

    不知道有哪位朋友也遇到过此类问题并解决了,或者告诉我发生这种状况的原因,谢谢!

    2012年10月19日 7:07

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