<!DOCTYPE html5><html lang="en"><head> <meta charset="UTF-8"> <title>CSS3-Canvas畫布(圖形-圓)</title> <script> window.onload=function () { var canvas=document.getElementById("canvas");//獲取canvas對象 var ctx=canvas.getContext("2d"); //建立二維的繪圖上下文對象 ctx.beginPath(); ctx.arc(100,75,50,0,2*Math.PI); //參數分別是(橫座標、縱座標、半徑、起始角(弧度計0.5PI/1PI/1.5PI/2PI)、結束角 、可選(False順時針,true逆時針)) ctx.stroke(); } </script></head><body><h2>Canvas畫布(圖形-圓)</h2><canvas id="canvas" width="500" height="500" style="border:1px solid red "> 瀏覽器不支持canvas</canvas></body></html>