C# capturing image from webcam

 

Last two days I've been looking for a way to capture an image from the webcam using C#. I'm pretty new in c# and I DO NOT want to use external third party libs, so I found two nice ways, but both seems to return almost the same error. I couldn't get any of them to work, so it would be really nice if you help me to get one of them running or help me to find alternative.

So the first way I found is using Windows WIA. I found the following code: 

CommonDialogClass dialog = new CommonDialogClass();
Device camera = dialog.ShowSelectDevice(WiaDeviceType.CameraDeviceType, true, false);
        // take the photo 
Item item = camera.ExecuteCommand(CommandID.wiaCommandTakePicture);
ImageFile image = (ImageFile)item.Transfer(FormatID.wiaFormatJPEG);
        // filename and saving 
image.SaveFile("Test.jpg");

this code seems to be exacly what I'm looking for, but I can't get it running, because I'm getting the following error on the second line: 

Exception from HRESULT: 0x80210015

The second way I found is using the Avicap32.dll with the following sample: 

http://www.timvw.be/wp-content/code/csharp/testavicap32.zip

but I'm getting on this code: 

Image image = ((CaptureDevice)cboDevices.SelectedItem).Capture();
image.Save(@"c:capture.png", ImageFormat.Png);

the following exception: NullReferenceException: Object reference not set to an instance of an object.

I think that both solution are causing problems because they can't find my camera, but I can use my camera in skype without any problems.

  • WIA is for stills, it's a sort of "API to work with scanners"; 0x80210015 is WIA_S_NO_DEVICE_AVAILABLE
  • AVICAP32 API name is "Video for Windows" which is really deprecated and obsolete, it might work out (compatibility is still here) but chances are high that it will take you nowhere

    • APIs to work with web cameras are:

  • DirectShow
  • Media Foundation

    • Both are native APIs and you might have hard time to interface them directly from C# code, however with DirectShow.NET (especially) and Media Foundation.NET you have wrappers for managed code. You can find more on using DirectShow.NET here:

  • Capturing frames from webcam using DirectShow.NET
  • DirectShow Library-How to capture image using directshow library without showing the webcam live images on the PictureBox or Panel
  • Get image from webcam

    • I tried multiple approaches, and the easiest approach for me was Emgu.cv(nuget package). 

            VideoCapture capture = new VideoCapture(); //create a camera capture
        Bitmap image = capture.QueryFrame().Bitmap; //take a picture

    That's it (as of API version 3.3.0)

    Old API Approach 

            Capture capture = new Capture(); //create a camera captue
        Bitmap image = capture.QueryFrame().Bitmap; //take a picture

    I recommend Aforge.net framework.

    It was able to implement videoCaptureDevice class used in the sample project: Snapshot Maker example to quickly create a image capturing dialog. It is a little slower than DirectShow Library-How to capture image using directshow library without showing the webcam live images on the PictureBox or Panel but it is stable and it is easy method for setting video and image resolutions from a supported device.

    The only issue I ran into is VideoCaptureDevice.SimulateTrigger() uses a bacjground thread to create an image from a video feed and returns the image on an event. Need to delegate method to prevent cross thread issues if you place the returned image on a winform control on the UI thread.

    Get the source from Snapshot Maker project from Aforge.net source SVN link.

    链接地址: http://www.djcxy.com/p/80996.html

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