cv.Mat is not a constructor opencv

I am getting this bug TypeError: cv.Mat is not a constructor

I tried doing almost everything can't find any solution on internet

Index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Hello OpenCV.js</title>
</head>
<body>
<h2>Hello OpenCV.js</h2>
<p id="status">OpenCV.js is loading...</p>
<div>
<img src="dd.jpg" style="display:none;" id ="img">
<canvas id = "videoInput" height="500" width="500"></canvas>
<canvas id = "canvasOutput" height="500" width="500"></canvas>

<script async type="text/javascript" src="index.js"></script>
<script async src="opencv.js" onload="onOpenCvReady();" type="text/javascript"></script>
</body>
</html>

index.js

  document.getElementById('status').innerHTML = 'OpenCV.js is ready.';
  let video = document.getElementById('videoInput');
  let src = new cv.Mat(video.height, video.width, cv.CV_8UC4);
  let dst = new cv.Mat(video.height, video.width, cv.CV_8UC4);
  let gray = new cv.Mat();
  let cap = new cv.VideoCapture(video);
  let faces = new cv.RectVector();
  let classifier = new cv.CascadeClassifier();

  // load pre-trained classifiers
  classifier.load('haarcascade_frontalface_default.xml');

  const FPS = 30;
  function processVideo() {
      try {
          if (!streaming) {
              // clean and stop.
              src.delete();
              dst.delete();
              gray.delete();
              faces.delete();
              classifier.delete();
              return;
          }
          let begin = Date.now();
          // start processing.
          cap.read(src);
          src.copyTo(dst);
          cv.cvtColor(dst, gray, cv.COLOR_RGBA2GRAY, 0);
          // detect faces.
          classifier.detectMultiScale(gray, faces, 1.1, 3, 0);
          // draw faces.
          for (let i = 0; i < faces.size(); ++i) {
              let face = faces.get(i);
              let point1 = new cv.Point(face.x, face.y);
              let point2 = new cv.Point(face.x + face.width, face.y + face.height);
              cv.rectangle(dst, point1, point2, [255, 0, 0, 255]);
          }
          cv.imshow('canvasOutput', dst);
          // schedule the next one.
          let delay = 1000/FPS - (Date.now() - begin);
          setTimeout(processVideo, delay);
      } catch (err) {
          utils.printError(err);
      }
  };

  // schedule the first one.
  setTimeout(processVideo, 0);
}

I am also importing opencv.js as i have a downloaded version of it. Guess theres some initialization problem , please help me solve it ...

回答1:

opencv.js loads and fires the onload event before it's really initialized. To wait until opencv.js is really ready, opencv.js provides a on hook "onRuntimeInitialized". Use it something like this:

function openCvReady() {
  cv['onRuntimeInitialized']=()=>{
    // do all your work here
  };
}

回答2:

I had the exact same issue here. My solution was different to the one suggested. It has more flexibility since your operations will not be limited to a certain method called in the beginning of your code.

Step 1: and it's a very important one, since it actually affected my code: Make sure there are no unrelated errors on loading the page. It disrupted the loading of opencv.js

Step 2: make sure you load the script synchronously.

<script src="<%= BASE_URL %>static/opencv.js" id="opencvjs"></script>

That was it for me. It worked perfectly from that point.