贝塞尔曲线 ：它可以是二次和三次方的形式，一般用于绘制复杂而有规律的形状。
方法：
quadraticCurveTo(cp1x, cp1y, x, y)
bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y)
参数 x 和 y 是终点坐标，cp1x 和 cp1y 是第一个控制点的坐标，cp2x 和 cp2y 是第二个的。
用贝塞尔曲线绘制聊天气泡
说明
用贝塞尔曲线绘制聊天气泡
代码
<html>
<head>
<!--[if IE]>
<script type="text/javascript" src="excanvas.js"></script>
<script type="text/javascript" src="excanvas.compiled.js"></script>
<![endif]-->
<script type="text/javascript">
function draw() {
var canvas = document.getElementById("cv");
if (canvas.getContext) {
var ctx = canvas.getContext("2d");
ctx.moveTo(75,25);
ctx.quadraticCurveTo(25,25,25,62.5);
ctx.quadraticCurveTo(25,100,50,100);
ctx.quadraticCurveTo(50,120,30,125);
ctx.quadraticCurveTo(60,120,65,100);
ctx.quadraticCurveTo(125,100,125,62.5);
ctx.quadraticCurveTo(125,25,75,25);
ctx.stroke();
}
}
</script>
<title>用贝塞尔曲线绘制聊天气泡</title>
</head>
<body onload="draw();" >
<canvas id="cv" width="150" height="150">
</canvas>
</body>
</html>
效果
用贝塞尔曲线绘制爱心
说明
用贝塞尔曲线绘制爱心
代码
<html>
<head>
<!--[if IE]>
<script type="text/javascript" src="excanvas.js"></script>
<script type="text/javascript" src="excanvas.compiled.js"></script>
<![endif]-->
<script type="text/javascript">
function draw() {
var canvas = document.getElementById("cv");
if (canvas.getContext) {
var ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.moveTo(75,40);
ctx.bezierCurveTo(75,37,70,25,50,25);
ctx.bezierCurveTo(20,25,20,62.5,20,62.5);
ctx.bezierCurveTo(20,80,40,102,75,120);
ctx.bezierCurveTo(110,102,130,80,130,62.5);
ctx.bezierCurveTo(130,62.5,130,25,100,25);
ctx.bezierCurveTo(85,25,75,37,75,40);
ctx.fill();
}
}
</script>
<title>用贝塞尔曲线绘制爱心</title>
</head>
<body onload="draw();" >
<canvas id="cv" width="150" height="150">
</canvas>
</body>
</html>
效果
绘制圆角矩形(自定义方法)
function roundedRect(ctx,x,y,width,height,radius){
ctx.beginPath();
ctx.moveTo(x,y+radius);
ctx.lineTo(x,y+height-radius);
ctx.quadraticCurveTo(x,y+height,x+radius,y+height);
ctx.lineTo(x+width-radius,y+height);
ctx.quadraticCurveTo(x+width,y+height,x+width,y+height-radius);
ctx.lineTo(x+width,y+radius);
ctx.quadraticCurveTo(x+width,y,x+width-radius,y);
ctx.lineTo(x+radius,y);
ctx.quadraticCurveTo(x,y,x,y+radius);
ctx.stroke();
}
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