为何黑色背景显示不出来

源自：4-1 画一片星空

<!DOCTYPE html>

<html>

<head>

</head>

<body>

该浏览器不支持canvas,请使用其他浏览器。

</canvas>

window.onload = function(){

var canvas = document.getElementById("canvas");

canvas.width = 800;

canvas.height = 800;

var context = canvas.getContext("2d");

context.fillStyle="black";

context.fillRect=(0,0,canvas.width,canvas.height);

// context.strokeRect=(0,0,canvas.width,canvas.height);

// context.stroke();

drawStar(context,300,100,400,400,30);

}

function drawStar(cxt,R,r,x,y,rot){

cxt.beginPath();

for(var i=0;i<5;i++){

cxt.lineTo(Math.cos((18+72*i-rot)/180*Math.PI)*R+x,-Math.sin((18+72*i-rot)/180*Math.PI)*R+y);

cxt.lineTo(Math.cos((54+72*i - rot)/180*Math.PI)*r+x,-Math.sin((54+72*i- rot)/180*Math.PI)*r+y);

}

cxt.closePath();

cxt.fillStyle = '#FB3';

cxt.strokeStyle = '#FD5';

cxt.lineJoin = 'round';

cxt.lineWidth = 3;

cxt.fill();

cxt.stroke();

}

</script>

</body>

</html>

提问者：慕桂英1607375 2018-06-04 15:30