<!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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