canvas简易画画板（PC端和移动端）
2017-06-15 本文已影响0人
璃_b11f
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Document</title>
<meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no"/>
<style type="text/css">
canvas {
border: 1px solid #ccc;
}
html{
overflow: hidden;
}
*{
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<input id="colorSelect" type="color" name="" value="" placeholder="">
<input type="submit" name="" value="清空画板" onclick="qingkong()">
<br>
<canvas width="500" height="500" id="canvas">
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</canvas>
</body>
<script>
var selector = document.getElementById("colorSelect");
// 声明color的全局变量
var color = null;
// 获取color的颜色
selector.onchange = function(){
color = this.value;
}
var canvas = document.getElementById("canvas");
var cxt = canvas.getContext("2d");
if(document.documentElement.clientWidth>768){
huaD();
qingkong();
}else{
huaS();
qingkong();
}
//当屏幕发生变化时触发
window.onresize = function(){
if(document.documentElement.clientWidth>768){
huaD();
qingkong();
}else{
huaS();
qingkong();
}
}
//pc端触发
function huaD(){
canvas.onmousedown = function(e){
// 获取canvas画面上的x y 轴
var x = e.clientX - canvas.offsetLeft;
var y = e.clientY - canvas.offsetTop;
cxt.beginPath();
cxt.moveTo(x,y);
canvas.onmousemove = function(e){
var x = e.clientX - canvas.offsetLeft;
var y = e.clientY - canvas.offsetTop;
cxt.lineTo(x,y);
cxt.strokeStyle=color;
cxt.stroke();
}
// 鼠标抬起事件 把上一个的move的事件清空
canvas.onmouseup = function(){
canvas.onmousemove = null;
}
}
}
//移动端触发
function huaS(){
canvas.addEventListener("touchstart", function(e){
var x = e.changedTouches[0].clientX - e.target.offsetLeft;
var y = e.changedTouches[0].clientY - e.target.offsetTop;
cxt.beginPath();
cxt.moveTo(x,y);
canvas.addEventListener("touchmove", function(e){
e.preventDefault();
var x = e.changedTouches[0].clientX - e.target.offsetLeft;
var y = e.changedTouches[0].clientY - e.target.offsetTop;
cxt.lineTo(x,y);
cxt.strokeStyle=color;
cxt.stroke();
}, false)
}, false)
}
//清空画板
function qingkong(){
cxt.clearRect(0,0,500,500);
console.log(11);
}
//禁止浏览器动来动去
document.body.addEventListener("touchmove", function(e){
e.preventDefault();
})
</script>
</html>
