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| <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>canvas - 数字签名</title>
<style>
canvas {
box-shadow: 0px 0px 5px #ccc;
border-radius: 8px;
}
div {
width: 450px;
box-shadow: 0px 0px 5px #ccc;
border-radius: 8px;
text-align: center;
}
</style>
</head>
<body>
<canvas id="canvas" width="450" height="300">
当前浏览器不支持canvas元素，请升级或更换浏览器！
</canvas>
<div id="clear">清空画布</div>
<script>
var canvas = document.getElementById('canvas');
var clear = document.getElementById('clear');
const ctx = canvas.getContext("2d");
canvas.addEventListener('mouseenter', () => {
canvas.addEventListener('mousedown', (e) => {
ctx.beginPath()
ctx.moveTo(e.offsetX, e.offsetY)
canvas.addEventListener('mousemove', draw)
})
canvas.addEventListener('mouseup', () => {
canvas.removeEventListener('mousemove', draw)
})
})
function draw(e) {
ctx.lineTo(e.offsetX, e.offsetY)
ctx.stroke()
}
clear.addEventListener('click', () => {
ctx.clearRect(0, 0, canvas.width, canvas.height);
})
</script>
</body>
</html>
|