HTML5 Canvas 绘制齿轮【每日一段代码34】
<!DOCTYPE html>
<html>
<head>
<title>HTML5 Canvas 绘制齿轮</title>
<script>
window.onload = function (){
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
//位置
var centerX = canvas.width/2;
var centerY = canvas.height/2;
//齿轮半径
var outerRadius = 95;
//齿轮交叉口半径
var innerRadius = 50;
//除去牙齿的齿轮半径
var midRadius = innerRadius*1.6;
//圆孔半径
var holeRadius = 10;
// NUM点是需要点的数量
//使轮齿。齿轮齿数
//等于一半的点数。在这个配方，
//我们将用时50分，这相当于25个齿轮齿。
var numPoints = 50;
//绘制齿轮的齿数
context.beginPath();
//设置的lineJoine属性圆滑，轮齿是平的。
context.lineJoin = "bevel";
//通过循环点的数量，以创建齿轮形状
for (var n=0; n<numPoints; n++)
{
var radius = null;
if (n%2==0)
{
radius = outerRadius;
}
else{
radius = innerRadius;
}
var theta = ((Math.PI*2)/numPoints)*(n+1);
var x = (radius*Math.sin(theta))+centerX;
var y = (radius*Math.cos(theta))+centerY;
if (n==0)
{
context.moveTo(x,y);
}
else {
context.lineTo(x,y);
}
}
context.closePath();
context.lineWidth = 5;
context.strokeStyle="#004CB3";
context.stroke();
context.beginPath();
context.arc(centerX,centerY,midRadius,0,Math.PI*2,false);
var grd = context.createLinearGradient(230,0,370,200);
grd.addColorStop(0,"#8ED6FF");
grd.addColorStop(1,"#004CB3");
context.fillStyle = grd;
context.fill();
context.lineWidth = 5;
context.strokeStyle="#004CB3";
context.stroke();
context.beginPath();
context.arc(centerX,centerY,holeRadius,0,Math.PI*2,false);
context.fillStyle = "white";
context.fill();
context.strokeStyle = "#004CB3";
context.stroke();
}
</script>
</head>
<body style="margin:100px 10px;">
<canvas id="myCanvas" width="600px" height="250" style="border:2px solid black;"></canvas>
</body>
</html>
显示效果如下：
实例为 canvas 绘图的一个综合应用。用到的知识包括，绘制圆形，线性渐变，lineJoin等。
实例来自网络。传送门：http://demo.cnmsdn.com/demo50.html
