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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Trackbar Example</title>
<link href="js_example_style.css" rel="stylesheet" type="text/css" />
</head>
<body>
<h2>Trackbar Example</h2>
<p>
<canvas> elements named <b>canvasInput1</b>, <b>canvasInput2</b> and <b>canvasOutput</b> have been prepared.<br>
The code of <textarea> will be executed when <input> element named <b>trackbar</b> value changes.<br>
You can change the code in the <textarea> to investigate more.
</p>
<div>
<textarea class="code" rows="12" cols="80" id="codeEditor" spellcheck="false">
</textarea>
<p class="err" id="errorMessage"></p>
</div>
<div>
<b>trackbar</b>
<input type="range" id="trackbar" disabled value="50" min="0" max="100" step="1">
<label id="weightValue" ></label>
<div>
<table cellpadding="0" cellspacing="0" width="0" border="0">
<tr>
<td>
<canvas id="canvasInput1" class="small"></canvas>
</td>
<td>
<canvas id="canvasInput2" class="small"></canvas>
</td>
<td>
<canvas id="canvasOutput" class="small"></canvas>
</td>
</tr>
<tr>
<td>
<div class="caption">canvasInput1</div>
</td>
<td>
<div class="caption">canvasInput2</div>
</td>
<td>
<div class="caption">canvasOutput</div>
</td>
</tr>
</table>
</div>
</div>
<script src="utils.js" type="text/javascript"></script>
<script id="codeSnippet" type="text/code-snippet">
let trackbar = document.getElementById('trackbar');
let alpha = trackbar.value/trackbar.max;
let beta = ( 1.0 - alpha );
let src1 = cv.imread('canvasInput1');
let src2 = cv.imread('canvasInput2');
let dst = new cv.Mat();
cv.addWeighted( src1, alpha, src2, beta, 0.0, dst, -1);
cv.imshow('canvasOutput', dst);
dst.delete();
src1.delete();
src2.delete();
</script>
<script type="text/javascript">
let utils = new Utils('errorMessage');
utils.loadCode('codeSnippet', 'codeEditor');
utils.loadImageToCanvas('apple.jpg', 'canvasInput1');
utils.loadImageToCanvas('orange.jpg', 'canvasInput2');
let trackbar = document.getElementById('trackbar');
trackbar.addEventListener('input', () => {
utils.executeCode('codeEditor');
});
let weightValue = document.getElementById('weightValue');
weightValue.innerText = trackbar.value;
trackbar.addEventListener('input', () => {
weightValue.innerText = trackbar.value;
});
utils.loadOpenCv(() => {
trackbar.removeAttribute('disabled');
utils.executeCode('codeEditor');
});
</script>
</body>
</html>
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