JQuery插件让图片旋转任意角度且代码极其简单

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);
    }