引入下方的jquery.rotate.js文件，然后通过$("选择器").rotate(角度);可以旋转任意角度，
例如$("#rotate-image").rotate(45);把这句放在$(document).ready(function(){ });中
就是将id为rotate-image的图片旋转45度。
不过，貌似在Chrome中总是不显示。
唉，找了两个小时，才发现Chrome太坑爹了，没法获取图片的长宽。
解决办法是，把$("#rotate-image").rotate(45);放在
$(window).load(function(){ });中，因为在Chrome中图片在执行$(document).ready(function(){ });中的语句时并没有加载完图片，坑爹啊。
另外可以更方便的通过调用$("选择器").rotateRight()和$("选择器").rotateLeft()来分别向右旋转90度和向左旋转90度。
jquery.rotate.js:
jQuery.fn.rotate = function(angle,whence) {
var p = this.get(0);
// 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.round(Math.cos(rotation) * 1000) / 1000;
var sintheta = Math.round(Math.sin(rotation) * 1000) / 1000;
//alert(costheta+","+sintheta);
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);
}
jQuery.fn.rotateRight = function(angle) {
this.rotate(angle==undefined?90:angle);
}
jQuery.fn.rotateLeft = function(angle) {
this.rotate(angle==undefined?-90:-angle);
}