Image Zoom in Javascript

I recently spent some time investigating how to achieve image zoom using Javascript (as Extjs doesn't support it as of v3). There may be simpler jquery or other ways to achieve this but I wanted some simple Javascript. Suppose we have a couple of synced Extjs images and panels defined as follows:

        /**
         * The first image (BoxComponent)
         */
        var imgBox1 = new Ext.ux.Image({
            id: 'img_box1',   
            src:'http://earthobservatory.nasa.gov/Features/BlueMarble/Images/land_shallow_topo_2048.jpg'
        });

       
        /**
         * Panel for the first image
         */
        var imgPanel1 = new Ext.Panel({
            id: 'img_panel1',
            title: "Migrated",
            height: 280,
            autoScroll: true,
            items:[imgBox1],
            listeners: {
                render: function(p){
                    //sync scrolling between image panel 1 and 2
                    p.body.on('scroll', function(e){
                        var panel2 = Ext.getCmp('img_panel2').body.dom;
                        panel2.scrollLeft = e.target.scrollLeft; 
                        panel2.scrollTop = e.target.scrollTop;
                    }, p);
                  }
                }
        });
       
        /**
         * The second image (BoxComponent)
         */
        var imgBox2 = new Ext.ux.Image({
            id: 'img_box2',
            src:'http://earthobservatory.nasa.gov/Features/BlueMarble/Images/land_shallow_topo_2048.jpg'
        });
       
        /**
         * Panel for the second image
         */
        var imgPanel2 = new Ext.Panel({
            id: 'img_panel2',
            title: "Stacked",
            height: 280,
            autoScroll: true,
            items:[imgBox2],
            listeners: {
                render: function(p){
                    //sync scrolling between image panel 1 and 2
                    p.body.on('scroll', function(e){
                        var panel1 = Ext.getCmp('img_panel1').body.dom;
                        panel1.scrollLeft = e.target.scrollLeft; 
                        panel1.scrollTop = e.target.scrollTop;
                    }, p);
                  }
                }
        });

Zoom can be achieved as follows:

    /**
     * Add zoom functionality to image panels
     */
    'addZoom': function() {
   
        var zooming=function(e){
            e=window.event ||e;
            var o=this,data=e.wheelDelta || -e.detail*40,zoom,size;
                
            //TODO: Zooming in IE doesn't zoom to the correct point?
            if(!+'\v1'){//IE
                var oldWidth=o.offsetWidth;
                var oldHeight=o.offsetHeight;       
   
                zoom = parseInt(o.style.zoom) || 100;
                zoom += data / 12;
                if(zoom > zooming.min)
                    o.style.zoom = zoom + '%';
                e.returnValue=false;
   
                var newWidth=o.offsetWidth*zoom/100;
                var newHeight=o.offsetHeight*zoom/100;
                var scrollLeft = (o.parentNode.scrollLeft/oldWidth)*newWidth;
                var scrollTop = (o.parentNode.scrollTop/oldHeight)*newHeight;
               
                o.parentNode.scrollLeft = scrollLeft;
                o.parentNode.scrollTop = scrollTop;
            }else {
                size=o.getAttribute("_zoomsize").split(",");
                zoom=parseInt(o.getAttribute("_zoom")) ||100;
                zoom+=data/12;
               
                var oldWidth=o.offsetWidth;
                var oldHeight=o.offsetHeight;
                var newWidth=size[0]*zoom/100;
                var newHeight=size[1]*zoom/100;
                var scrollLeft = (o.parentNode.scrollLeft/oldWidth)*newWidth;
                var scrollTop = (o.parentNode.scrollTop/oldHeight)*newHeight;  
   
                if(zoom>zooming.min){
                    o.setAttribute("_zoom",zoom);
                    o.style.width=newWidth+"px";
                    o.style.height=newHeight+"px";
                    //TODO: Zoom is very jerky when setting scrollbars this way, when
                    // either scrollbar is not at position 0. Need to fix it.
                    o.parentNode.scrollLeft = scrollLeft;
                    o.parentNode.scrollTop = scrollTop;
                }
                e.preventDefault();
                e.stopPropagation();//for firefox3.6
            }
        };
   
        zooming.add=function(obj,min){// obj = image box, min defines the minimum image zoom size ,defaults to 50
            zooming.min=min || 50;
            obj.onmousewheel=zooming;
            if(/Firefox/.test(navigator.userAgent))//if Firefox
                obj.addEventListener("DOMMouseScroll",zooming,false);
            if(-[1,]){//if not IE
                    obj.setAttribute("_zoomsize",obj.naturalWidth+","+obj.naturalHeight);
            }
        };
       
        zooming.add(document.getElementById("img_box1"));  
        zooming.add(document.getElementById("img_box2"));      
    }

The above zoom function is as far as I got with it before having to put it aside. As you may notice from the comments, it doesn't work that nicely in IE and setting of the scrollbars is quite jerky when setting both scrollLeft and scrollTop to somthing other than position 0. This is something I will need to investigate further and update here in future.