基於HTML5 canvas的畫箭頭組件(轉)

時間 2019-12-11

原文原文鏈接

/**
 * 實現兩點間畫箭頭的功能
 * @author mapleque@163.com
 * @version 1.0
 * @date 2013.05.23
 */
(function(window,document){
	if (window.mapleque==undefined)
		window.mapleque={};
	if (window.mapleque.arrow!=undefined)
		return;
	
	/**
	 * 組件對外接口
	 */
	var proc={
		/**
		 * 接收canvas對象，並在此上畫箭頭（箭頭起止點已經設置）
		 * @param context
		 */
		paint:function(context){paint(this,context);},
		/**
		 * 設置箭頭起止點
		 * @param sp起點
		 * @param ep終點
		 * @param st強度
		 */
		set:function(sp,ep,st){init(this,sp,ep,st);},
		/**
		 * 設置箭頭外觀
		 * @param args
		 */
		setPara:function(args){
			this.size=args.arrow_size;//箭頭大小
			this.sharp=args.arrow_sharp;//箭頭銳鈍
		}
	};
	
	var init=function(a,sp,ep,st){
		a.sp=sp;//起點
		a.ep=ep;//終點
		a.st=st;//強度
	};
	var paint=function(a,context){
		var sp=a.sp;
		var ep=a.ep;
		if (context==undefined)
			return;
		//畫箭頭主線
		context.beginPath();
		context.moveTo(sp.x,sp.y);
		context.lineTo(ep.x,ep.y);
		//畫箭頭頭部
		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();
	};
	//計算頭部座標
	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
				};
	};
	//旋轉座標
	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);

<!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">請使用支持HTML5的瀏覽器</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>

效果還不錯，不滿意能夠本身調試javascript