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canvas-star6-drawMoon.html

2015-11-20 17:47 330 查看

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<canvas id="canvas" style="margin:0 auto;border:1px #ddd solid;">
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 = 800;
canvas.height = 800;

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

// context.arc(400,400,300,0.5*Math.PI,1.5*Math.PI,true);
// context.moveTo(400,100);
// context.arcTo(1200,400,400,700,(400-100)*dis(400,100,1200,400)/(1200-400))
// context.stroke();

fillMoon(context,2,400,400,300,0)

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

function dis(x1,y1,x2,y2){
return Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))
}

// 优化
// x,y位置 r半径
function fillMoon(cxt,d,x,y,R,rot,fillColor){
cxt.save();
cxt.translate(x,y);
cxt.rotate(rot*Math.PI/180);
cxt.scale(R,R);
pathMoon(cxt,d);
cxt.fillStyle = fillColor || "#fb5";
cxt.fill();
cxt.restore();
}

function pathMoon(cxt,d){
cxt.beginPath();
cxt.arc(0,0,1,0.5*Math.PI,1.5*Math.PI,true);
moveTo(0,-1);
cxt.arcTo(d,0,0,1,dis(0,-1,d,0)/d);
// 或者使用贝塞尔二次曲线
// cxt.quadraticCurveTo(1.2,0,0,1)
cxt.closePath();
}

function dis(x1,y1,x2,y2){
return Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))
}
</script>
</body>
</html>

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