HTML5 canvas 怎么画半圆

Question

这个弧度怎么画

Answer 1

贝塞尔曲线

var canvas=document.getElementById('canvas');
var context=canvas.getContext('2d');           

//绘制2次贝塞尔曲线  
context.beginPath();  
context.moveTo(20,150);  
context.quadraticCurveTo(150,40,280,150); 
context.strokeStyle = "red"; 
context.stroke();

Answer 2

http://www.uml.org.cn/html/20...

Answer 3

先translate，然后moveto，再arc就可以。画个扇形