源码：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>对勾，二次方贝塞尔曲线</title> </head> <body> <p>这是用三条二次方贝塞尔曲线构成的复选框标记对号<input type="checkbox" checked></p> <canvas id="canvas" width="400" height="400"></canvas> </body> <script> var canvas = document.getElementById('canvas'), context = canvas.getContext('2d'); context.strokeStyle = '#3aa112'; context.shadowColor = 'rgba(50,50,50,1.0)'; context.shadowOffsetX = 3; context.shadowOffsetY = 3; context.shadowBlur = 4; context.lineWidth=20; context.lineCap='round'; context.beginPath(); //设定开始点(120.5,130) context.moveTo(120.5,130); //设定控制点(150.8,130)和结束点(160.6,150.5); context.quadraticCurveTo(150.8,130,160.6,150.5); context.quadraticCurveTo(190,250,210.5,160.5); context.quadraticCurveTo(240,100.5,290,70.5); context.stroke(); </script> </html>
