uosotm/index.html

## index.html
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Hello OpenCV.js</title>
  </head>
  <body>
    <input type="file" id="input" name="file" />
    <canvas id="output"></canvas>

    <script src="https://docs.opencv.org/3.4.0/opencv.js"></script>
    <script>
      const image = new Image();
      const input = document.getElementById('input');

      input.addEventListener('change', (e) => {
        image.src = URL.createObjectURL(e.target.files[0]);
      }, false);

      image.onload = function() {
        const src = cv.imread(image);
        const dst = new cv.Mat();

        cv.cvtColor(src, dst, cv.COLOR_RGBA2GRAY, 0);
        cv.imshow('output', dst);

        src.delete(); dst.delete();
      }
    </script>
  </body>
</html>
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Hello OpenCV.js</title>
	</head>
	<body>
	<input type="file" id="input" name="file" />
	<canvas id="output"></canvas>

	<script src="https://docs.opencv.org/3.4.0/opencv.js"></script>
	<script>
	const image = new Image();
	const input = document.getElementById('input');

	input.addEventListener('change', (e) => {
	image.src = URL.createObjectURL(e.target.files[0]);
	}, false);

	image.onload = function() {
	const src = cv.imread(image);
	const dst = new cv.Mat();

	cv.cvtColor(src, dst, cv.COLOR_RGBA2GRAY, 0);
	cv.imshow('output', dst);

	src.delete(); dst.delete();
	}
	</script>
	</body>
	</html>