1 使用jQueryRotate.js實現
示例代碼：
複製代碼代碼如下:
<!DOCTYPE html>
<html>
<head>
<title></title>
<style type="text/css">
#div1 {
width: 800px;
height: 600px;
background-color: #ff0;
position: absolute;
}
.imgRotate {
width: 100px;
height: 80px;
position: absolute;
top: 50%;
left: 50%;
margin: -40px 0 0 -50px;
}
</style>
</head>
<body>
<div id="div1">
<img id="img1" src="http://www.baidu.com/img/logo-yy.gif" />
<input id="input2" type="button" value="btn2"></input>
</div>
</body>
<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript" src="jQueryRotate.js"></script>
<script type="text/javascript">
var num = 0;
$("#input2").click(function(){
num ++;
$("#img1").rotate(90*num);
});
</script>
</html>
測試結果：chrome下效果正常，旋轉後img對象仍為img對象；ie8下效果正常，但旋轉後img對像變為下面對象，由於對像變化，若旋轉後仍按原來方法獲取img對象，則會報js錯誤。欲獲取image對象，可根據class獲取。如果圖像旋轉後，不進行其它操作，則可用此方法。若進行其它操作，如放大、縮小圖像，則此方法實現較複雜。
複製代碼代碼如下:
<span ...>
<rvml:group...>
<rvml:image.../>
</rvml:group>
</span>
2 使用Microsoft提供的Matrix對象
示例代碼：
複製代碼代碼如下:
<!DOCTYPE html>
<html>
<head>
<title></title>
<style type="text/css">
#div1 {
width: 800px;
height: 600px;
background-color: #ff0;
position: absolute;
}
.imgRotate {
width: 100px;
height: 100px;
position: absolute;
top: 50%;
left: 50%;
margin: -50px 0 0 -50px;
}
#imgRotate {
width: 100px;
height: 100px;
position: absolute;
top: 50%;
left: 50%;
margin: -50px 0 0 -50px;
}
</style>
</head>
<body>
<div id="div1">
<img id="img1" src="http://www.baidu.com/img/logo-yy.gif" />
<input id="input1" type="button" value="btn1"></input>
</div>
</body>
<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript">
function rotate(id,angle,whence) {
var p = document.getElementById(id);
// we store the angle inside the image tag for persistence
if (!whence) {
p.angle = ((p.angle==undefined?0:p.angle) + angle) % 360;
} else {
p.angle = angle;
}
if (p.angle >= 0) {
var rotation = Math.PI * p.angle / 180;
} else {
var rotation = Math.PI * (360+p.angle) / 180;
}
var costheta = Math.cos(rotation);
var sintheta = Math.sin(rotation);
if (document.all && !window.opera) {
var canvas = document.createElement('img');
canvas.src = p.src;
canvas.height = p.height;
canvas.width = p.width;
canvas.style.filter = "progid:DXImageTransform.Microsoft.Matrix(M11="+costheta+",M12="+(-sintheta)+",M21="+sintheta+",M22="+costheta+",SizingMethod=' auto expand')";
} else {
var canvas = document.createElement('canvas');
if (!p.oImage) {
canvas.oImage = new Image();
canvas.oImage.src = p.src;
} else {
canvas.oImage = p.oImage;
}
canvas.style.width = canvas.width = Math.abs(costheta*canvas.oImage.width) + Math.abs(sintheta*canvas.oImage.height);
canvas.style.height = canvas.height = Math.abs(costheta*canvas.oImage.height) + Math.abs(sintheta*canvas.oImage.width);
var context = canvas.getContext('2d');
context.save();
if (rotation <= Math.PI/2) {
context.translate(sintheta*canvas.oImage.height,0);
} else if (rotation <= Math.PI) {
context.translate(canvas.width,-costheta*canvas.oImage.height);
} else if (rotation <= 1.5*Math.PI) {
context.translate(-costheta*canvas.oImage.width,canvas.height);
} else {
context.translate(0,-sintheta*canvas.oImage.width);
}
context.rotate(rotation);
context.drawImage(canvas.oImage, 0, 0, canvas.oImage.width, canvas.oImage.height);
context.restore();
}
canvas.id = p.id;
canvas.angle = p.angle;
p.parentNode.replaceChild(canvas, p);
}
function rotateRight(id,angle) {
rotate(id,angle==undefined?90:angle);
}
function rotateLeft(id,angle) {
rotate(id,angle==undefined?-90:-angle);
}
$("#input1").click(function(){
$("img.imgRotate").attr("id","imgRotate");
rotateLeft("imgRotate",90);
$("#imgRotate").attr("top","50%");
$("#imgRotate").attr("left","50%");
$("#imgRotate").attr("margin","-50px 0 0 -50px");
});
</script>
</html>
測試結果：chrome下效果正常，但旋轉後img對像變為canvas對象；ie8下效果正常，旋轉後img對象仍為img對象。 Matrix()參數較多，使用時需較多計算。
3 使用Microsoft提供的BasicImage對象
示例代碼：
複製代碼代碼如下:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</head>
<body>
<img id="image" src="http://www.baidu.com/img/logo-yy.gif" />
<input id="input2" type="button" value="btn2"></input>
</body>
<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript">
var num = 0;
$("#input2").click(function(){
num = (num + 1) % 4;
document.getElementById('image').style.filter = 'progid:DXImageTransform.Microsoft.BasicImage(rotation='+num+')';
});
</script>
</html>
測試結果：chrome下不能旋轉；ie8下效果正常，旋轉後img對象仍為img對象。 BasicImage()僅一個參數。
查看這三種方法的代碼會發現，本質上是一種解決方案：chrome下使用canvas對象實現，ie8下使用VML或者Matrix()或BasicImage()實現。本人近期改造一個組件：其中涉及到旋轉、放大圖片，由於jQueryRotate.js在ie8下會生成一個新的對象，導致放大圖片前選擇圖片時，需要進行特殊處理。後決定對chrome、ie8分開處理，chrome下使用jQueryRotate實現，ie8下使用BasicImage()實現，保證了代碼的簡潔性和可讀性。