我正在尝试使用 Canvas 绘制星星，但代码未运行。我想了解:测量Y和X坐标的步骤是什么？如何找到他们？绘制任何形状？
<html>
<head>
<meta charset = "utf-8">
<title>Drawing Lines</title>
</head>
<body>
<canvas id = "drawLines" width = "400" height = "200"
style = "border: 1px solid Black;">
</canvas>
<script>
var canvas = document.getElementById("drawLines");
var context = canvas.getContext("2d")
canvas.beginPath();
canvas.moveTo(50,50);
canvas.lineTo(120,150);
canvas.lineTo(0,180);
canvas.lineTo(120,210);
canvas.lineTo(50,310);
canvas.lineTo(160,250);
canvas.lineTo(190,370);
canvas.lineTo(220,250);
canvas.lineTo(330,310);
canvas.lineTo(260,210);
canvas.lineTo(380,180);
canvas.closePath();
canvas.stroke();
</script>
</body>
</html>
最佳答案
星星基本上是一个规则的多边形，在内半径和外半径上有交替的点。
下面是一个绘制星形的灵活函数示例。
您可以设置尖峰的位置、#spikes 和内外半径:
示例代码和演示:http://jsfiddle.net/m1erickson/8j6kdf4o/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; }
canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
function drawStar(cx,cy,spikes,outerRadius,innerRadius){
var rot=Math.PI/2*3;
var x=cx;
var y=cy;
var step=Math.PI/spikes;
ctx.beginPath();
ctx.moveTo(cx,cy-outerRadius)
for(i=0;i<spikes;i++){
x=cx+Math.cos(rot)*outerRadius;
y=cy+Math.sin(rot)*outerRadius;
ctx.lineTo(x,y)
rot+=step
x=cx+Math.cos(rot)*innerRadius;
y=cy+Math.sin(rot)*innerRadius;
ctx.lineTo(x,y)
rot+=step
}
ctx.lineTo(cx,cy-outerRadius);
ctx.closePath();
ctx.lineWidth=5;
ctx.strokeStyle='blue';
ctx.stroke();
ctx.fillStyle='skyblue';
ctx.fill();
}
drawStar(100,100,5,30,15);
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=300 height=300></canvas>
</body>
</html>
关于javascript - 如何使用 canvas HTML5 绘制星星？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25837158/