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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Image Area Example</title>
<link href="js_example_style.css" rel="stylesheet" type="text/css" />
</head>
<body>
<h2>Image Area Example</h2>
<p>
<canvas> elements named <b>canvasInput</b> have been prepared.<br>
Click <b>Try it</b> button to see the result. You can choose another image.<br>
You can change the code in the <textarea> to investigate more.
</p>
<div>
<div class="control"><button id="tryIt" disabled>Try it</button></div>
<textarea class="code" rows="9" cols="100" id="codeEditor" spellcheck="false">
</textarea>
<p class="err" id="errorMessage"></p>
</div>
<div>
<div>
<canvas id="canvasInput"></canvas>
<div class="caption">canvasInput <input type="file" id="fileInput" name="file" accept="image/*" /></div>
</div>
<div>
<p><strong>The area is: </strong><span id="areaOutput"></span></p>
</div>
</div>
<script src="utils.js" type="text/javascript"></script>
<script id="codeSnippet" type="text/code-snippet">
let src = cv.imread('canvasInput');
let dst = cv.Mat.zeros(src.rows, src.cols, cv.CV_8UC3);
cv.cvtColor(src, src, cv.COLOR_RGBA2GRAY, 0);
cv.threshold(src, src, 177, 200, cv.THRESH_BINARY);
let contours = new cv.MatVector();
let hierarchy = new cv.Mat();
cv.findContours(src, contours, hierarchy, cv.RETR_CCOMP, cv.CHAIN_APPROX_SIMPLE);
let cnt = contours.get(20);
// You can try more different parameters
let area = cv.contourArea(cnt, false);
areaOutput.innerHTML = area;
src.delete(); dst.delete(); contours.delete(); hierarchy.delete(); cnt.delete();
</script>
<script type="text/javascript">
let utils = new Utils('errorMessage');
utils.loadCode('codeSnippet', 'codeEditor');
utils.loadImageToCanvas('lena.jpg', 'canvasInput');
utils.addFileInputHandler('fileInput', 'canvasInput');
let tryIt = document.getElementById('tryIt');
tryIt.addEventListener('click', () => {
utils.executeCode('codeEditor');
});
utils.loadOpenCv(() => {
tryIt.removeAttribute('disabled');
});
</script>
</body>
</html>