canvas 手写毛笔字效果

2024年5月15日 319次阅读 
<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8" />
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
	<title> canvas 手写毛笔字效果 </title>
<style type="text/css">
#canvasId {
	background-color: #FFFFcc;
}
</style>
</head>
<body>

<canvas id="canvasId" width="700" height="500"></canvas><br />
<input type="button" value="clear" onclick="hw.clear();" />

<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)";
	var _this = this;
	this.canvas.onmousedown = function (e) { _this.downEvent(e)};
	this.canvas.onmousemove = function (e) { _this.moveEvent(e)};
	this.canvas.onmouseup = function (e) { _this.upEvent(e)};
	this.canvas.onmouseout = function (e) { _this.upEvent(e)};
	this.moveFlag = false;
	this.upof = {};
	this.radius = 0;
	this.has = [];
	this.lineMax = 30;
	this.lineMin = 3;
	this.linePressure = 1;
	this.smoothness = 80;
}

Handwriting.prototype.clear = function () {
	this.ctx.clearRect(0,0,this.canvas.width,this.canvas.height);
}

Handwriting.prototype.downEvent = function (e) {
	this.moveFlag = true;
	this.has = [];
	this.upof = this.getXY(e);
}

Handwriting.prototype.moveEvent = function (e) {
	if (!this.moveFlag)
		return;
	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 (this.has.length<=4)
		return;
	var len = Math.round(this.has[0].dis/2)+1;
	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();
	}
}

Handwriting.prototype.upEvent = function (e) {
	this.moveFlag = false;
}

Handwriting.prototype.getXY = function (e)
{
	return {
		x : e.clientX - this.canvas.offsetLeft + (document.body.scrollLeft || document.documentElement.scrollLeft),
		y : e.clientY - 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 = 2.5;
hw.smoothness = 100;

</script>
</body>
</html>

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