Capture Image From Webcam Video Using HTML5 Using JavaScript And Upload To Server Using C#

Darshan Shah
Apr 15, 2023

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Today I am going to show you how to capture images from the webcam using JavaScript and HTML5 and upload on the server using a simple Ajax call using C#.

For your reference, I have attached zip file of the MVC project with this article.

Below are the steps needed to create this example.

Access Webcam, which requires user permission
Once you have permission, then capture the image on Canvas
Make a Fetch call to send Image to Server with the help of Base64 data
And upload Base64 data as an image on the server folder

In this demo, we will upload the image to the server using an ASP.NET API.

So let's get started.

HTML

<div class="jumbotron" style="margin-top:20px;padding:20px;">    
  <p><span id="errorMsg"></span></p>    
  <div class="row">    
    <div class="col-lg-6">    
      <!-- Here we stream video from the webcam -->    
      <h4>    
        Video coming from Webcam  
        <button class="btn btn-primary" id="btnCapture">Capture to Canvas >></button>    
      </h4>    
      <video id="video" playsinline autoplay alt="Webcam video stream"></video>    
    </div>    
    
    <div class="col-lg-6">    
      <h4>    
        Captured image from Webcam 
        <button type="submit" class="btn btn-primary" id="btnSave" name="btnSave">Save the canvas (image) to server</button>    
      </h4>    
      <!-- Webcam video snapshot -->    
      <canvas id="canvas" width="475" height="475" alt="Canvas image"></canvas>    
    </div>    
  </div>    
</div>

Scripts


  const video = document.querySelector("#video");

  // Basic settings for the video to get from Webcam
  const constraints = {
    audio: false,
    video: {
      width: 475,
      height: 475
    }
  };

  // This condition will ask permission to user for Webcam access
  if (navigator.mediaDevices.getUserMedia) {
    navigator.mediaDevices.getUserMedia(constraints)
      .then(function(stream) {
        video.srcObject = stream;
      })
      .catch(function(err0r) {
        console.log("Something went wrong!");
      });
  }

  function stop(e) {
    const stream = video.srcObject;
    const tracks = stream.getTracks();

    for (let i = 0; i < tracks.length; i++) {
      const track = tracks[i];
      track.stop();
    }
    video.srcObject = null;
  }


  // Below code to capture image from Video tag (Webcam streaming)
  const btnCapture = document.querySelector("#btnCapture");
  const canvas = document.getElementById('canvas');

  btnCapture.addEventListener('click', function() {
    const context = canvas.getContext('2d');
    // Capture the image into canvas from Webcam streaming Video element
    context.drawImage(video, 0, 0);
  });

  // Upload image to server - ajax call - with the help of base64 data as a parameter
  const btnSave = document.querySelector("#btnSave");

  btnSave.addEventListener('click', async function() {
    // Below new canvas to generate flip/mirror image from existing canvas
    const destinationCanvas = document.createElement("canvas");
    const destCtx = destinationCanvas.getContext('2d');

    destinationCanvas.height = 500;
    destinationCanvas.width = 500;

    destCtx.translate(video.videoWidth, 0);
    destCtx.scale(-1, 1);
    destCtx.drawImage(document.getElementById("canvas"), 0, 0);

    // Get base64 data to send to server for upload
    let imagebase64data = destinationCanvas.toDataURL("image/png");
    imagebase64data = imagebase64data.replace('data:image/png;base64,', '');

    try {
      const response = await fetch('/Home/UploadWebCamImage', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json; charset=utf-8'
        },
        body: JSON.stringify({
          imageData: imagebase64data
        })
      });

      if (response.ok) {
        alert('Image uploaded successfully..');
      } else {
        throw new Error(`Request failed with status ${response.status}`);
      }
    } catch (error) {
      console.error('Error while uploading image:', error);
    }
  });

Below is the condition which actually asks the user for Webcam permission.

if (navigator.mediaDevices.getUserMedia)  {

...

}

CSS

/* Flipping the video as it was not mirror view */
video {
  transform: scaleX(-1);
  margin-top: 5px;
}

/* Flipping the canvas image as it was not mirror view */
#canvas {
  transform: scaleX(-1);
  filter: FlipH;
}

Note

We need to add the CSS to flip the video and canvas as the webcam is not showing mirror video.

C# Code

public async Task<string> UploadWebCamImage(string imageData)
{
    string filename = Server.MapPath("~/UploadWebcamImages/webcam_") + DateTime.Now.ToString().Replace("/", "-").Replace(" ", "_").Replace(":", "") + ".png";

    byte[] data = Convert.FromBase64String(imageData);

    using (FileStream fs = new FileStream(filename, FileMode.Create))
    {
        await fs.WriteAsync(data, 0, data.Length);
    }

    return "success";
}

So once all the setup is done and we run the project. First, the user has to give permission for the site to use the Webcam, shown below.