IE 透明 无效 js

我们在做图片渐变显示的时候，给图片设置透明的在IE里边失效。

导致的原因是图片没有设置高宽，解决办法也就是给图片设置高宽即可。

下面是一个效果的JS代码，红颜色部分代码如果删掉在IE里面就不会有渐变效果。

function g(id){
    if(!id)return;
    if(typeof id =="string"){
        return document.getElementById(id);
    };
    return id;
};

var banner2 = {
    init:function(){
        var that = this;
        this.menu  = g("bannerMenu");
        this.img = g("bannerImgUl");
        this.li = this.menu.getElementsByTagName("li");
        var ulHtml = [];
        for(var i = 0;i<this.li.length;i++){
            var src = this.li[i].getAttribute("src");
                this.li[i].num = i;
            var liHTML = "<li><img src='"+src+"' />";
                ulHtml.push(liHTML);
                
                this.li[i].onmouseover = function(){
                    if(this.num == that.c)return;
                    that.c = this.num;
                    that.show();
                }
        };
        this.img.innerHTML = ulHtml.join("");
        this.imgLi = this.img.getElementsByTagName("li");
        for(var t = 0;t<this.imgLi.length;t++){
            this.imgLi[t].style.width = this.imgLi[t].offsetWidth;
            this.imgLi[t].style.height = this.imgLi[t].offsetHeight;
        }
        this.c = 0;
        this.old = 0;
        //this.imgLi[this.c].style.display = "block";
        this.show();
    },
    show:function(){
        var that= this;
        this.imgLi[this.old].style.display = "none";
        this.imgLi[this.c].style.display = "block";
        
        if(document.all){
                that.imgLi[that.c].style.filter = "Alpha(opacity=0)";
            }else{
                that.imgLi[that.c].style.opacity = 0;
        };
        var opacity = 0;        
        clearInterval(that.autoId);
        this.autoId = setInterval(function(){
            opacity+=10;
            if(opacity==100){
                clearInterval(that.autoId);
            };
            if(document.all){
                that.imgLi[that.c].style.filter = "Alpha(opacity="+opacity+")";
            }else{
                that.imgLi[that.c].style.opacity = opacity/100;
            };
        },30);        
        this.li[this.old].className = " ";
        this.li[this.c].className = "hover";
        this.old = this.c;
    }
}