如何从WMV视频创建缩略图

Question

如何从WMV视频创建缩略图

c#.netimagevideovideo-processing

3

我希望在网站上列出视频的缩略图，想要从视频中获取单个帧（从特定时间）并将其显示为缩略图。使用 .Net（C# 或 VB）可以实现吗？

- Michel

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Gray Area · Accepted Answer

是的，这是可能的。您需要使用DirectShow.NET。我找到了这个链接很有用。

编辑：

好的，看起来自从我使用它以来库已经改变了...该死的开源 :)

我刚刚翻译成以下代码并测试，对我来说运行良好（请注意，它假定在c:\aaa中有一个wmv文件名为C4.wmv，并且输出将进入c:\aaa\out.bmp）。

IGraphBuilder graphbuilder = (IGraphBuilder)new FilterGraph();
      ISampleGrabber samplegrabber = (ISampleGrabber) new SampleGrabber();
      graphbuilder.AddFilter((IBaseFilter)samplegrabber, "samplegrabber");

      AMMediaType mt = new AMMediaType();
      mt.majorType = MediaType.Video;
      mt.subType = MediaSubType.RGB24;
      mt.formatType = FormatType.VideoInfo;
      samplegrabber.SetMediaType(mt);

      int hr = graphbuilder.RenderFile("C:\\aaa\\c4.wmv", null);

      IMediaEventEx mediaEvt = (IMediaEventEx)graphbuilder;
      IMediaSeeking mediaSeek = (IMediaSeeking)graphbuilder;
      IMediaControl mediaCtrl = (IMediaControl)graphbuilder;
      IBasicAudio basicAudio = (IBasicAudio)graphbuilder;
      IVideoWindow videoWin = (IVideoWindow)graphbuilder;

      basicAudio.put_Volume(-10000);
      videoWin.put_AutoShow(OABool.False);

      samplegrabber.SetOneShot(true);
      samplegrabber.SetBufferSamples(true);

      long d = 0;
      mediaSeek.GetDuration(out d);
      long numSecs = d / 10000000;

      long secondstocapture = (long)(numSecs * 0.10f);


      DsLong rtStart, rtStop;
      rtStart = new DsLong(secondstocapture * 10000000);
      rtStop = rtStart;
      mediaSeek.SetPositions(rtStart, AMSeekingSeekingFlags.AbsolutePositioning, rtStop, AMSeekingSeekingFlags.AbsolutePositioning);

      mediaCtrl.Run();
      EventCode evcode;
      mediaEvt.WaitForCompletion(-1, out evcode);

      VideoInfoHeader videoheader = new VideoInfoHeader();
      AMMediaType grab = new AMMediaType();
      samplegrabber.GetConnectedMediaType(grab);
      videoheader =
      (VideoInfoHeader)Marshal.PtrToStructure(grab.formatPtr,
      typeof(VideoInfoHeader));


      int width = videoheader.SrcRect.right;
      int height = videoheader.SrcRect.bottom;
      Bitmap b = new Bitmap(width, height, PixelFormat.Format24bppRgb);

      uint bytesPerPixel = (uint)(24 >> 3);
      uint extraBytes = ((uint)width * bytesPerPixel) % 4;
      uint adjustedLineSize = bytesPerPixel * ((uint)width + extraBytes);
      uint sizeOfImageData = (uint)(height) * adjustedLineSize;


      BitmapData bd1 = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
      int bufsize = (int)sizeOfImageData;
      int n = samplegrabber.GetCurrentBuffer(ref bufsize, bd1.Scan0);
      b.UnlockBits(bd1);
      b.RotateFlip(RotateFlipType.RotateNoneFlipY);
      b.Save("C:\\aaa\\out.bmp");
      Marshal.ReleaseComObject(graphbuilder);
      Marshal.ReleaseComObject(samplegrabber);

请注意，DirectShow在某种程度上处于悬而未决的状态...微软公司建议您使用Media Foundation。我是一位老派的DirectX程序员，现在基本没有使用了。