JQuery插件让图片旋转任意角度且代码极其简单

    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);  
    }