C# Webcam Barcode Reader: A DirectShow.NET Implementation

In today’s fast-paced digital world, the ability to quickly and accurately capture data is paramount. Barcode scanning has emerged as a reliable and efficient solution for automating data entry across various applications. This tutorial explores webcam barcode reading on Windows, demonstrating how to build a powerful barcode detection application using C#, the DirectShow.NET library, and the Dynamsoft Barcode Reader SDK. DirectShow.NET captures video streams from a webcam, while the Dynamsoft Barcode Reader SDK decodes the barcodes.

DirectShow.NET Webcam barcode reader

Prerequisites

Opening Webcam and Streaming Video with DirectShow.NET

The DirectShow.NET sample Samples\Capture\PlayCap demonstrates how to open a webcam and display the video stream in C#. Follow these steps:

  1. Get connected devices.

     DsDevice[] devices = DsDevice.GetDevicesOfCat(FilterCategory.VideoInputDevice);

  2. Create a filter graph and a capture graph.

     int hr = 0;
 this.graphBuilder = (IFilterGraph2)new FilterGraph();
 this.captureGraphBuilder = (ICaptureGraphBuilder2)new CaptureGraphBuilder2();
 this.mediaControl = (IMediaControl)this.graphBuilder;
 this.videoWindow = (IVideoWindow)this.graphBuilder;
 DsError.ThrowExceptionForHR(hr);

  3. Set the filter graph to the capture graph.

     hr = this.captureGraphBuilder.SetFiltergraph(this.graphBuilder);
 DsError.ThrowExceptionForHR(hr);

  4. Bind the moniker to a filter object.

     int hr = 0;
 IEnumMoniker classEnum = null;
 IMoniker[] moniker = new IMoniker[1];
 object source = null;
    
 ICreateDevEnum devEnum = (ICreateDevEnum)new CreateDevEnum();
    
 hr = devEnum.CreateClassEnumerator(FilterCategory.VideoInputDevice, out classEnum, 0);
 DsError.ThrowExceptionForHR(hr);
    
 Marshal.ReleaseComObject(devEnum);
    
 if (classEnum == null)
 {
     throw new ApplicationException("No video capture device was detected.\r\n\r\n" +
                                     "This sample requires a video capture device, such as a USB WebCam,\r\n" +
                                     "to be installed and working properly.  The sample will now close.");
 }
    
 if (classEnum.Next(moniker.Length, moniker, IntPtr.Zero) == 0)
 {
     Guid iid = typeof(IBaseFilter).GUID;
     moniker[0].BindToObject(null, null, ref iid, out source);
 }
 else
 {
     throw new ApplicationException("Unable to access video capture device!");
 }
    
 Marshal.ReleaseComObject(moniker[0]);
 Marshal.ReleaseComObject(classEnum);
    
 return (IBaseFilter)source;

  5. Add a camera source to the graph.

     hr = this.graphBuilder.AddFilter(sourceFilter, "Video Capture");
 DsError.ThrowExceptionForHR(hr);

  6. Configure a sample grabber and set a callback function for the video stream.

     sampleGrabber = new SampleGrabber() as ISampleGrabber;
    
 {
             AMMediaType media;
             int hr;
             media = new AMMediaType();
             media.majorType = MediaType.Video;
             media.subType = MediaSubType.RGB24;
             media.formatType = FormatType.VideoInfo;
             hr = sampleGrabber.SetMediaType(media);
             DsError.ThrowExceptionForHR(hr);
             DsUtils.FreeAMMediaType(media);
             media = null;
             hr = sampleGrabber.SetCallback(this, 1);
             DsError.ThrowExceptionForHR(hr);
 }

 hr = this.graphBuilder.AddFilter(sampleGrabber as IBaseFilter, "Frame Callback");
 DsError.ThrowExceptionForHR(hr);

  7. Configure the video stream format.

     private void SetConfigParams(ICaptureGraphBuilder2 capGraph, IBaseFilter capFilter, int iFrameRate, int iWidth, int iHeight)
 {
     int hr;
     object config;
     AMMediaType mediaType;
     // Find the stream config interface
     hr = capGraph.FindInterface(
         PinCategory.Capture, MediaType.Video, capFilter, typeof(IAMStreamConfig).GUID, out config);
    
     IAMStreamConfig videoStreamConfig = config as IAMStreamConfig;
     if (videoStreamConfig == null)
     {
         throw new Exception("Failed to get IAMStreamConfig");
     }
    
     // Get the existing format block
     hr = videoStreamConfig.GetFormat(out mediaType);
     DsError.ThrowExceptionForHR(hr);
    
     // copy out the videoinfoheader
     VideoInfoHeader videoInfoHeader = new VideoInfoHeader();
     Marshal.PtrToStructure(mediaType.formatPtr, videoInfoHeader);
    
     // if overriding the framerate, set the frame rate
     if (iFrameRate > 0)
     {
         videoInfoHeader.AvgTimePerFrame = 10000000 / iFrameRate;
     }
    
     // if overriding the width, set the width
     if (iWidth > 0)
     {
         videoInfoHeader.BmiHeader.Width = iWidth;
     }
    
     // if overriding the Height, set the Height
     if (iHeight > 0)
     {
         videoInfoHeader.BmiHeader.Height = iHeight;
     }
    
     // Copy the media structure back
     Marshal.StructureToPtr(videoInfoHeader, mediaType.formatPtr, false);
    
     // Set the new format
     hr = videoStreamConfig.SetFormat(mediaType);
     DsError.ThrowExceptionForHR(hr);
    
     DsUtils.FreeAMMediaType(mediaType);
     mediaType = null;
 }

  8. Render the video stream.

     hr = this.captureGraphBuilder.RenderStream(PinCategory.Preview, MediaType.Video, sourceFilter, (sampleGrabber as IBaseFilter), null);
 DsError.ThrowExceptionForHR(hr);

  9. Output the video stream to a PictureBox and resize the video window position.

     int hr = 0;
 hr = this.videoWindow.put_Owner(pictureBox1.Handle);
 DsError.ThrowExceptionForHR(hr);
    
 hr = this.videoWindow.put_WindowStyle(WindowStyle.Child);
 DsError.ThrowExceptionForHR(hr);
    
 hr = this.videoWindow.put_Visible(OABool.True);
 DsError.ThrowExceptionForHR(hr);
    
 Rectangle rc = pictureBox1.ClientRectangle;
 hr = videoWindow.SetWindowPosition(0, 0, _previewWidth, _previewHeight);
 DsError.ThrowExceptionForHR(hr);

  10. Start the video stream.

    rot = new DsROTEntry(this.graphBuilder);
hr = this.mediaControl.Run();
DsError.ThrowExceptionForHR(hr);

Asynchronously Reading Barcodes with Dynamsoft Barcode Reader v9.x

  1. Create a barcode reader instance in Form1():

     using Dynamsoft.DBR;

 private Dynamsoft.DBR.BarcodeReader _barcodeReader;

 public Form1()
 {
     InitializeComponent();
    
     // Initialize Dynamsoft Barcode Reader
     string errorMsg;
     EnumErrorCode errorCode = Dynamsoft.DBR.BarcodeReader.InitLicense("LICENSE-KEY", out errorMsg);
     if (errorCode != EnumErrorCode.DBR_SUCCESS)
     {
         Console.WriteLine(errorMsg);
     }
     _barcodeReader = new Dynamsoft.DBR.BarcodeReader();
 }

  2. To avoid blocking the UI thread, use asynchronous barcode reading in the callback function.

     public int BufferCB(double SampleTime, IntPtr pBuffer, int BufferLen)
 {
     Bitmap v = new Bitmap(_previewWidth, _previewHeight, _previewStride,
         PixelFormat.Format24bppRgb, pBuffer);
     v.RotateFlip(RotateFlipType.Rotate180FlipX);
     if (isFinished)
     {   
         this.BeginInvoke((MethodInvoker)delegate
         {
             isFinished = false;
             ReadBarcode(v);
             isFinished = true;
         });
     }
     return 0;
 }

 private void ReadBarcode(Bitmap bitmap)
 {
     Bitmap nonIndexedBitmap = EnsureNonIndexedFormat(bitmap);
    
     TextResult[] results = _barcodeReader.DecodeBitmap(nonIndexedBitmap, "");
     textBox1.Clear();
    
     if (results != null)
     {
         using (Graphics g = Graphics.FromImage(nonIndexedBitmap))
         {
             foreach (TextResult result in results)
             {
                 string output = "Text: " + result.BarcodeText + Environment.NewLine + "Format: " + result.BarcodeFormatString + Environment.NewLine;
                 Point[] points = result.LocalizationResult.ResultPoints;
    
                 // Draw lines based on four points
                 for (int i = 0; i < points.Length; i++)
                 {
                     Point p1 = points[i];
                     Point p2 = points[(i + 1) % points.Length];
                     g.DrawLine(new Pen(Color.Red, 3), p1, p2);
                 }
    
                 textBox1.AppendText(output);
             }
         }
    
         if (!isCameraMode)
         {
             pictureBox1.Image = nonIndexedBitmap;
         }
     }
     else
     {
         textBox1.AppendText("No barcode detected!" + Environment.NewLine);
     }
 }

Using Dynamsoft Barcode Reader v10.x for Barcode Decoding

The Dynamsoft Barcode Reader SDK v10.x introduces a new architecture and API. The following steps demonstrate how to use the new version for barcode decoding:

  1. Create a barcode reader instance in Form1():

     using Dynamsoft.DBR;
 using Dynamsoft.Core;
 using Dynamsoft.CVR;
 using Dynamsoft.License;

 private CaptureVisionRouter cvr;

 public Form1()
 {
     InitializeComponent();
    
     string errorMsg;
     int errorCode = LicenseManager.InitLicense("LICENSE-KEY", out errorMsg);
     if (errorCode != (int)EnumErrorCode.EC_OK)
         Console.WriteLine("License initialization error: " + errorMsg);
        
     cvr = new CaptureVisionRouter();
 }

  2. Retrieve the bitmap data and convert it to ImageData for barcode decoding:

     private void ReadBarcode(Bitmap bitmap)
 {
     Bitmap nonIndexedBitmap = EnsureNonIndexedFormat(bitmap);
    
     // Convert Bitmap to ImageData
     byte[] bytes;  
     int width;
     int height;
     int stride;
     PixelFormat pixelFormat; 
     GetBitmapData(nonIndexedBitmap, out bytes, out width, out height, out stride, out pixelFormat);
    
     EnumImagePixelFormat format = EnumImagePixelFormat.IPF_RGB_888;
     switch (pixelFormat)
     {
         case PixelFormat.Format24bppRgb:
             format = EnumImagePixelFormat.IPF_RGB_888;
             break;
         case PixelFormat.Format32bppArgb:
             format = EnumImagePixelFormat.IPF_ARGB_8888;
             break;
         default:
             MessageBox.Show("Unsupported pixel format.");
             return;
     }
    
     ImageData data = new ImageData(bytes, width, height, stride, format);
     CapturedResult result = cvr.Capture(data, PresetTemplate.PT_READ_BARCODES);
    
     textBox1.Clear();
     if (result == null)
     {
         MessageBox.Show("No barcode detected.");
     }
     else if (result.GetErrorCode() != 0)
     {
         MessageBox.Show("Error: " + result.GetErrorCode() + ", " + result.GetErrorString());
     }
     else
     {
         DecodedBarcodesResult barcodesResult = result.GetDecodedBarcodesResult();
         if (barcodesResult != null)
         {
             BarcodeResultItem[] items = barcodesResult.GetItems();
             foreach (BarcodeResultItem barcodeItem in items)
             {
                 Console.WriteLine("Result " + (Array.IndexOf(items, barcodeItem) + 1));
                 Console.WriteLine("Barcode Format: " + barcodeItem.GetFormatString());
                 Console.WriteLine("Barcode Text: " + barcodeItem.GetText());
             }
    
             using (Graphics g = Graphics.FromImage(nonIndexedBitmap))
             {
                 foreach (BarcodeResultItem barcodeItem in items)
                 {
                     string output = "Text: " + barcodeItem.GetFormatString() + Environment.NewLine + "Format: " + barcodeItem.GetFormatString() + Environment.NewLine;
                     Dynamsoft.Core.Point[] points = barcodeItem.GetLocation().points;
    
                     // Draw lines based on four points
                     for (int i = 0; i < points.Length; i++)
                     {
                         Dynamsoft.Core.Point p1 = points[i];
                         Dynamsoft.Core.Point p2 = points[(i + 1) % points.Length];
                         g.DrawLine(new Pen(Color.Red, 3), p1[0], p1[1], p2[0], p2[1]);
                     }
    
                     textBox1.AppendText(output);
                 }
             }
    
             if (!isCameraMode)
             {
                 pictureBox1.Image = nonIndexedBitmap;
             }
         }
         else
         {
             textBox1.AppendText("No barcode detected!" + Environment.NewLine);
         }
     }
 }

Source Code

https://github.com/yushulx/DirectShow.NET-Webcam-Barcode-Reader