使用Html5中的cavas画一面国旗

var canvas = document.getElementById("canvas");//创建一个cavas画板    var context = canvas.getContext('2d');//设置画板属性    var width=canvas.width;    var height=width*2/3;    context.fillStyle="red";    context.fillRect(0,0,width,height);    var maxR = 0.15, minR = 0.05;    var maxX = 0.55, maxY = 0.35;//大五星的位置    var minX = [0.80, 0.90, 0.90, 0.80,0.65,0.50,0.40];//各个小五角星的x坐标    var minY = [0.20, 0.30, 0.45, 0.55,0.60,0.60,0.50];//各个小五角星的y坐标    var ox = height * maxX, oy = height * maxY;

<canvas id="canvas" width="600" height="400"></canvas>   

create5star(context,ox,oy,height * maxR,"#ff0",0);//绘制大五角星    for (var idx = 0; idx < 7; idx++) {        var  sx = minX[idx] * height, sy = minY[idx] * height;        var  theta = Math.atan((oy - sy)/(ox - sx));        create5star(context,sx, sy, height * minR, "#ff0",-Math.PI/2+theta);    // 画小五角星    }    //绘制五角星    function create5star(context,sx,sy,radius,color,rotato){        context.save();        context.fillStyle=color;        context.translate(sx,sy);//移动坐标原点        context.rotate(Math.PI+rotato);//旋转        context.beginPath();//创建路径        var x = Math.sin(0);        var y= Math.cos(0);        var dig = Math.PI/5 *4;        for(var i = 0;i< 5;i++){//画五角星的五条边            var x = Math.sin(i*dig);            var y = Math.cos(i*dig);            context.lineTo(x*radius,y*radius);        }        context.closePath();        context.stroke();        context.fill();        context.restore();    }