使用Image遇到的問題：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript" src="http:///keleyi/pmedia/jquery/jquery-1.11.1.min.js"></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">
浏覽器不支持
</canvas>
</body>
</html>
其實這種寫法是有錯誤的，實際上只要一刷新圖片就不顯示出來。要想保證刷新正常顯示需要在Image onload的時候重繪一次才行。測試在chrome 19下會出現的問題。
解決方案
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript" src="http:///keleyi/pmedia/jquery/jquery-1.11.1.min.js"></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">
浏覽器不支持
</canvas>
</body>
</html>