webturing
/
ChineseHandWritingApp


			
				
					
						
						
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							<!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" οnclick="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>