样例：
废话少说，直接上代码：
arrow.js
/** * 实现两点间画箭头的功能 * @author [email protected] * @version 1.0 * @date 2013.05.23 */;(function(window,document){ if (window.mapleque==undefined) window.mapleque={}; if (window.mapleque.arrow!=undefined) return; /** * 组件对外接口 */ var proc={ /** * 接收canvas对象，并在此上画箭头（箭头起止点已经设置） * @param context */ paint:function(context){paint(this,context);}, /** * 设置箭头起止点 * @param sp起点 * @param ep终点 * @param st强度 */ set:function(sp,ep,st){init(this,sp,ep,st);}, /** * 设置箭头外观 * @param args */ setPara:function(args){ this.size=args.arrow_size;//箭头大小 this.sharp=args.arrow_sharp;//箭头锐钝 } }; var init=function(a,sp,ep,st){ a.sp=sp;//起点 a.ep=ep;//终点 a.st=st;//强度 }; var paint=function(a,context){ var sp=a.sp; var ep=a.ep; if (context==undefined) return; //画箭头主线 context.beginPath(); context.moveTo(sp.x,sp.y); context.lineTo(ep.x,ep.y); //画箭头头部 var h=_calcH(a,sp,ep,context); context.moveTo(ep.x,ep.y); context.lineTo(h.h1.x,h.h1.y); context.moveTo(ep.x,ep.y); context.lineTo(h.h2.x,h.h2.y); context.stroke(); }; //计算头部坐标 var _calcH=function(a,sp,ep,context){ var theta=Math.atan((ep.x-sp.x)/(ep.y-sp.y)); var cep=_scrollXOY(ep,-theta); var csp=_scrollXOY(sp,-theta); var ch1={x:0,y:0}; var ch2={x:0,y:0}; var l=cep.y-csp.y; ch1.x=cep.x+l*(a.sharp||0.025); ch1.y=cep.y-l*(a.size||0.05); ch2.x=cep.x-l*(a.sharp||0.025); ch2.y=cep.y-l*(a.size||0.05); var h1=_scrollXOY(ch1,theta); var h2=_scrollXOY(ch2,theta); return { h1:h1, h2:h2 }; }; //旋转坐标 var _scrollXOY=function(p,theta){ return { x:p.x*Math.cos(theta)+p.y*Math.sin(theta), y:p.y*Math.cos(theta)-p.x*Math.sin(theta) }; }; var arrow=new Function(); arrow.prototype=proc; window.mapleque.arrow=arrow;})(window,document);
arrow.html
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>sample of the arrow</title><script type="text/javascript" src="./arrow.js"></script></head><body><canvas width=800 height=600 id="arrowLine">请使用支持HTML5的浏览器</canvas><script type="text/javascript">var cont=document.getElementById("arrowLine").getContext('2d');var a1=new window.mapleque.arrow();a1.set({x:350,y:300},{x:200,y:200});a1.paint(cont);var a2=new window.mapleque.arrow();a2.set({x:100,y:100},{x:200,y:250});a2.paint(cont);var a3=new window.mapleque.arrow();a3.set({x:100,y:300},{x:150,y:150});a3.paint(cont);var a4=new window.mapleque.arrow();a4.set({x:350,y:150},{x:150,y:250});a4.setPara({ arrow_size:0.5, arrow_sharp:0.5})a4.paint(cont);</script></body></html>