html5 canvas 画直线箭头

大家好，最近在研究页面的动态效果，可是，搞了半天还是搞砸了。。。没有动态，只有静态。记录备份一下！

	
		
		
	
	
	
		

			
整体感知训练
	 		
		
		
 
	

//画线
    arrow_line("can",250,250,0,0,200,0);   //横  （向右）
    arrow_line("can",0,0,0,0,0,200);   //竖 (向下)  
    arrow_line("can",-200,0,200,0,0,0);   //横  （向左）
    arrow_line("can",200,-200,0,200,0,0);   //竖 (向上) 
    arrow_line("can",0,0,0,200,150,50);   //右斜上
    arrow_line("can",0,0,0,200,150,350);   //右斜下
    arrow_line("can",-200,50,200,150,50,10);   //左斜上
    arrow_line("can",0,0,200,150,50,300);   //左斜下