学步园

我的IR项目里要对视频文件进行预览，目前还没有解决，以下的方法是一个尝试。

在system32下，有一个qedit.dll文件，这是DirectShow的一个COM组件（DS大部份都是COM组件），就是说我们可以直接以COM的形式引用到C＃项目里。

我做了一个简单测试项目。先把qedit.dll找到，然后以COM注册到项目中。对MediaDet类进行了一个简单的封装，然后运行一个测试项目：
运行结果（从AVI中提取第10桢的内容）：

部份代码：仅供参考：

MediaDetector类
using System;
using System.IO;
using DexterLib;
using System.Drawing;
using System.Drawing.Imaging;

namespace PublicLibrary
{
    /**//// <summary>
    /// Summary description for MediaDetector.
    /// </summary>
    public class MediaDetector
    {
        //fields
        protected MediaDetClass _MediaDet;
        protected Image.GetThumbnailImageAbort _ImageCallback;
        //events
        public event ErrorHandler OnError;
        //properties
        protected MediaDetClass MediaDecteor
        {
            get
            {
                if(this._MediaDet==null)
                {
                    try
                    {
                        this._MediaDet = new MediaDetClass();
                    }
                    catch(Exception ex)
                    {
                        this.FileErrorEvent(ex);
                    }
                }
                return _MediaDet;
            }
        }
        protected Image.GetThumbnailImageAbort ImageCallback
        {
            get
            {
                if(this._ImageCallback == null)
                {
                    this._ImageCallback = new Image.GetThumbnailImageAbort(ThumbnailCallback);
                }
                return this._ImageCallback;
            }
        }

        //methods
        private void FileErrorEvent(Exception i_ex)
        {
            if(this.OnError!=null)
            {
                try
                {
                    this.OnError(this,i_ex);
                }
                catch(Exception ex)
                {
                    System.Diagnostics.Trace.WriteLine(ex.Message);
                }
            }
        }
        /**//// <summary>
        /// Method to get thumbinal image from media file.
        /// </summary>
        /// <param name="i_MediaFile">Media file full path and name.</param>
        /// <param name="i_Size">Image size.</param>
        /// <param name="i_type">Media type</param>
        /// <param name="i_Stream">If the media type is video, this parameter is the video's stream to grab and create image.</param>
        /// <returns></returns>
        public Image GetThumbnail(string i_MediaFile,Size i_Size,MediaTypes i_type,int i_Stream)
        {
            switch(i_type)
            {
                default:
                case MediaTypes.Unknow:
                    this.FileErrorEvent(new Exception("Unknow media type."));
                    return null;
                case MediaTypes.Audio:
                    this.FileErrorEvent(new Exception("This media type has not implemented to create an image."));
                    return null;
                case MediaTypes.Image:
                    return this.GetThumbnailFromImage(i_MediaFile,i_Size);
                case MediaTypes.Video:
                    return this.GetThumbnailFromVideo(i_MediaFile,i_Size,i_Stream);
            }
        }

        public Image GetThumbnailFromImage(string i_MediaFile,Size i_Size)
        {
            try
            {
                Image m_image = Image.FromFile(i_MediaFile);
                return m_image.GetThumbnailImage(i_Size.Width,i_Size.Height,this.ImageCallback,IntPtr.Zero);
            }
            catch(Exception ex)
            {
                this.FileErrorEvent(ex);
                return null;
            }
        }

        public Image GetThumbnailFromVideo(string i_MediaFile,Size i_Size,int i_Stream)
        {
            this.MediaDecteor.Filename = i_MediaFile;
            this.MediaDecteor.CurrentStream = 0;
            //int m_ImageSize = (int)this.MediaDecteor.StreamLength;
            try
            {
                this.MediaDecteor.WriteBitmapBits(i_Stream,i_Size.Width,i_Size.Height,"Temp.bmp");
                Stream m_stream = File.Open("Temp.bmp",FileMode.Open,FileAccess.Read,FileShare.None);
                byte[] m_bytes = new byte[m_stream.Length];
                m_stream.Read(m_bytes,0,m_bytes.Length);
                m_stream.Close();
                File.Delete("Temp.bmp");
                MemoryStream m_MemoStream = new MemoryStream(m_bytes.Length);
                m_MemoStream.Write(m_bytes,0,m_bytes.Length);
                return Image.FromStream(m_MemoStream);
            }
            catch(Exception ex)
            {
                this.FileErrorEvent(ex);
                return null;
            }
        }

        private bool ThumbnailCallback()
        {
            return false;
        }
        //ctor
        public MediaDetector()
        {            
        }
    }

    public class MediaHelper#region public class MediaHelper
    public class MediaHelper
    {
        static public MediaTypes ConvertToMediaType(int i_Type)
        {
            switch(i_Type)
            {
                default:
                case 0:
                    return MediaTypes.Unknow;
                case 1:
                    return MediaTypes.Image;
                case 2:
                    return MediaTypes.Video;
                case 3:
                    return MediaTypes.Audio;
            }
        }

        static public MediaTypes ConvertToMediaType(string i_Type)
        {
            switch(i_Type.ToLower())
            {
                default:
                case "unknow":
                    return MediaTypes.Unknow;
                case "image":
                    return MediaTypes.Image;
                case "video":
                    return MediaTypes.Video;
                case "audio":
                    return MediaTypes.Audio;
            }
        }
    }
    #endregion

    public delegate void ErrorHandler(object i_Sender,Exception i_ex);
    public enum MediaTypes
    {
        Image = 1,
        Video = 2,
        Audio = 3,
        Unknow = 0,
    }

}

测试Form代码：

Form类
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
//
using PublicLibrary;

namespace Country.Study
{
    /**//// <summary>
    /// Summary description for Thumbinal.
    /// </summary>
    public class Thumbnail : System.Windows.Forms.Form
    {
        private MediaDetector _MediaDetector;
        //
        private MediaDetector MediaDetector