用 lineTo画出来的线有锯齿，怎么才能变得圆润一些？

window.onload = function()
        {
            drawXY.init();
            
            for(var i = 0 ; i < arr.length ; i ++)
            {
                drawXY.start(arr[i]);
            }
        };
        
        var arr = [
           {"x" : 0 , "y" : 120.5},
           {"x" : 10.5 , "y" : 108.5},
           {"x" : 20.5 , "y" : 80.5},
           {"x" : 30.5 , "y" : 78.5},
           {"x" : 40.5 , "y" : 68.5},
           {"x" : 50.5 , "y" : 58.5},
           {"x" : 60.5 , "y" : 50.5},
           {"x" : 70.5 , "y" : 48.5},
           {"x" : 150.5 , "y" : 30.5},
           {"x" : 160.5 , "y" : 20.5},
           {"x" : 180.5 , "y" : 18.5},
           {"x" : 230.5 , "y" : 17.5},
        ];
        
        var drawXY = {
            
            //canves对象
            myCanves : null,
            //canves宽度
            canvesWidth : null,
            //canves 2d对象
            ctx : null,
            
            //初始化
            init : function()
            {
                this.myCanves = document.getElementById("can");
                this.ctx = can.getContext("2d");
                this.ctx.globalCompositeOperation = "source-atop";
                this.ctx.canvas.width  = parseInt(window.innerWidth) - 80;
                this.canvesWidth = this.ctx.canvas.width;
                this.ctx.strokeStyle = "#f8b22f";
                this.ctx.lineWidth = 1;
                
                this.ctx.beginPath();
                this.ctx.moveTo(0,120);
            },
            
            /**
             * 开始绘制
             * @param {Object} obj
             */
            start : function(obj)
            {
                var self = this;
                self.ctx.lineTo(obj.x,obj.y);
                self.ctx.lineJoin = "round";
//                this.ctx.globalCompositeOperation = 'source-atop';
                self.ctx.stroke();
            },
        };