使用Image遇到的问题：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title></title> <script src="js/jquery-1.9.1.min.js" type="text/javascript" charset="utf-8"></script> <script type="text/javascript"> $(function() { var jsCanv = document.getElementById("canv"); var oCanv = jsCanv.getContext("2d"); var img = new Image(); img.src = "img.png"; oCanv.drawImage(img, 220, 30); }) </script> </head> <body> <canvas id="canv" width="500" height="500"> 浏览器不支持 </canvas> </body> </html>
其实这种写法是有错误的，实际上只要一刷新图片就不显示出来。要想保证刷新正常显示需要在Image onload的时候重绘一次才行。测试在chrome 19下会出现的问题。
解决方案
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title></title> <script src="js/jquery-1.9.1.min.js" type="text/javascript" charset="utf-8"></script> <script type="text/javascript"> $(function() { var jsCanv = document.getElementById("canv"); var oCanv = jsCanv.getContext("2d"); var img = new Image(); img.src = "img.png"; img.onload = function() { oCanv.drawImage(img, 220, 30); } }) </script> </head> <body> <canvas id="canv" width="500" height="500"> 浏览器不支持 </canvas> </body> </html>