<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<meta name="viewport" content="width=400">
<title> canvas手写毛笔字效果 </title>
<style type="text/css">
body {
margin: 0;
padding: 0;
background-color: #999999;
}
h1 {
text-align: center;
}
#canvasId {
background-color: #FFFFcc;
}
.button {
width: 100px;
height: 40px;
}
</style>
</head>
<body>
<h1>手写毛笔字效果-手机版</h1>
<canvas id="canvasId" width="400" height="400"></canvas><br />
<input type="button" value="全部清除" class="button" onclick="hw.clear();" />
<input type="button" value="清除最后一笔" class="button" onclick="hw.historyBack();" />
<script type="text/javascript">
function Handwriting(id) {
this.canvas = document.getElementById(id);
this.ctx = this.canvas.getContext("2d");
this.ctx.fillStyle = "rgba(0,0,0,0.25)";
this.canvas.addEventListener("touchstart", this.downEvent.bind(this), false);
this.canvas.addEventListener("touchmove", this.moveEvent.bind(this), false);
this.canvas.addEventListener("touchend", this.upEvent.bind(this), false);
this.canvas.addEventListener("contextmenu", function(e){ e.preventDefault() }, false);
//this.canvas.onmousedown = this.downEvent.bind(this);
//this.canvas.onmousemove = this.moveEvent.bind(this);
//this.canvas.onmouseup = this.upEvent.bind(this);
//this.canvas.onmouseout = this.upEvent.bind(this);
this.moveFlag = false;
this.upof = {};
this.radius = 0;
this.has = [];
this.startOf = null;
this.lineMax = 30;
this.lineMin = 3;
this.linePressure = 1;
this.smoothness = 80;
this.history = [];
}
Handwriting.prototype.clear = function () {
this.history = [];
this.ctx.clearRect(0,0,this.canvas.width,this.canvas.height);
}
Handwriting.prototype.historyBack = function () {
this.history.pop();
this.ctx.clearRect(0,0,this.canvas.width,this.canvas.height);
for (var i = 0; i < this.history.length; i++) {
var h = this.history[i];
for (var j = 0; j < h.length; j+=3) {
this.ctx.beginPath();
this.ctx.arc(h[j],h[j+1],h[j+2],0,2*Math.PI,true);
this.ctx.fill();
}
}
}
Handwriting.prototype.downEvent = function (e) {
this.moveFlag = true;
this.has = [];
this.history.push([]);
this.upof = this.getXY(e);
this.startOf = this.upof;
}
Handwriting.prototype.moveEvent = function (e) {
if (!this.moveFlag)
return;
e.preventDefault();
var of = this.getXY(e);
var up = this.upof;
var ur = this.radius;
this.has.unshift({time:new Date().getTime() ,dis:this.distance(up,of)});
var dis = 0;
var time = 0;
for (var n = 0; n < this.has.length-1; n++) {
dis += this.has[n].dis;
time += this.has[n].time-this.has[n+1].time;
if (dis>this.smoothness)
break;
}
var or = Math.min(time/dis*this.linePressure+this.lineMin , this.lineMax) / 2;
this.radius = or;
this.upof = of;
if (dis<7)
return;
if (this.startOf) {
up = this.startOf;
ur = or;
this.startOf = null;
}
var len = Math.ceil(this.distance(up,of)/2);
for (var i = 0; i < len; i++) {
var x = up.x + (of.x-up.x)/len*i;
var y = up.y + (of.y-up.y)/len*i;
var r = ur + (or-ur)/len*i;
this.ctx.beginPath();
this.ctx.arc(x,y,r,0,2*Math.PI,true);
this.ctx.fill();
this.history[this.history.length-1].push(x,y,r);
}
}
Handwriting.prototype.upEvent = function (e) {
this.moveFlag = false;
}
Handwriting.prototype.getXY = function (e) {
var x = e.touches[0].clientX;
var y = e.touches[0].clientY;
//var x = e.clientX;
//var y = e.clientY;
return {
x : x - this.canvas.offsetLeft + (document.body.scrollLeft || document.documentElement.scrollLeft),
y : y - this.canvas.offsetTop + (document.body.scrollTop || document.documentElement.scrollTop)
}
}
Handwriting.prototype.distance = function (a,b) {
var x = b.x-a.x , y = b.y-a.y;
return Math.sqrt(x*x+y*y);
}
var hw = new Handwriting("canvasId");
hw.lineMax = 40;
hw.lineMin = 5;
hw.linePressure = 3.1;
hw.smoothness = 100;
</script>
</body>
</html>
在线演示：https://js-game.github.io/Handwriting/handwriting.html
