<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
#out{
border: 1px solid red;
}
</style>
</head>
<body>
<canvas id="out" height="500" width="500"></canvas>
<button id="huihua">绘画</button>
<button id="cachu">橡皮擦</button>
<button id="chongzhi">重置</button>
</body>
<script>
var cvs = document.getElementById("out")
var huihua = document.getElementById("huihua")
var cachu = document.getElementById("cachu")
var chongzhi = document.getElementById("chongzhi")
var ctx = cvs.getContext("2d")
chongzhi.onclick = function(){
ctx.clearRect(0,0,cvs.width,cvs.height)
}
cachu.onclick=function(){
cvs.onmousedown=function(){
document.onmousemove=function(e){
ctx.clearRect(e.clientX-cvs.offsetLeft,e.clientY-cvs.offsetTop,20,20)
}
document.onmouseup=function(){
document.onmousedown=null;
document.onmousemove=null;
}
}
}
huihua.onclick = function () {
cvs.onmousedown=function(e){
ctx.beginPath()
ctx.moveTo(e.clientX-cvs.offsetLeft,e.clientY-cvs.offsetTop)
document.onmousemove=function(e){
ctx.lineTo(e.clientX-cvs.offsetLeft,e.clientY-cvs.offsetTop)
ctx.strokeStyle="red"
ctx.stroke()
}
document.onmouseup=function(){
document.onmousedown=null;
document.onmousemove=null;
}
}
}
</script>
</html>
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