canvas贝塞尔曲线

实现用贝塞尔曲线画一个气泡

html部分

1	<canvas id="canvas" width="300" height="300" width="300" style="border: 1px dashed #808080"></canvas>

js部分

function $$ (id) {  
    return document.getElementById(id)
}
window.onload = function () {  
    var can = $$('canvas')  
    var cxt = can.getContext('2d')  
    cxt.moveTo(75, 25)  
    cxt.quadraticCurveTo(25, 25, 25, 62)  
    cxt.quadraticCurveTo(25, 100, 50, 100)  
    cxt.quadraticCurveTo(50, 120, 30, 125)  
    cxt.quadraticCurveTo(60, 120, 65, 100)  
    cxt.quadraticCurveTo(125, 100, 125, 62)  
    cxt.quadraticCurveTo(125, 25, 75, 25)  
    cxt.strokeStyle = 'blue'  
    cxt.stroke()
}

气泡就这么画出来了
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