canvas-star0.html 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <canvas id="canvas" style="margin:0 auto;">
        The current browser does not support Canvas, can replace the browser a try!
    </canvas>

    <script>

        window.onload = function(){
            var canvas = document.getElementById('canvas');

            canvas.width = 1024;
            canvas.height = 768;

            if(canvas.getContext('2d')){
                var context = canvas.getContext('2d');

                
            
                context.lineWidth = 10;
                drawStar(context,200,300,400,400,30)
                

            }else{
                alert('当前游览器不支持Canvas，请更换游览器后再试！');
            }
        }

        // x,y是偏移量 rot 偏移量
        function drawStar(cxt,r,R,x,y,rot){
            cxt.beginPath();
            for(var i=0;i<5;i++){
                //假设大圆内径300
                cxt.lineTo(Math.cos( (18+i*72 - rot) / 180 * Math.PI )*R+x,
                                -Math.sin( (18+i*72 - rot) / 180 * Math.PI )*R+y);
                //假设小圆内径150
                cxt.lineTo(Math.cos( (54+i*72 - rot) / 180 * Math.PI )*r+x,
                                -Math.sin( (54+i*72 - rot) / 180 * Math.PI )*r+y);
            }
            cxt.closePath();
            cxt.stroke();
        }
    </script>
</body>
</html>

 

posted @ 2015-11-19 17:30  Cynthia娆墨旧染  阅读(197)  评论(0)  编辑  收藏  举报