用JS得到图片的大小及长、宽

<script>var img=null;function s(){if(img)img.removeNode(true);img=document.createElement("img");img.style.position="absolute";img.style.visibility="hidden";img.attachEvent("onreadystatechange",orsc);img.attachEvent("onerror",oe);document.body.insertAdjacentElement("beforeend",img);img.src=inp.value;}function oe(){alert("cant load img");}function orsc(){if(img.readyState!="complete")return false;alert(img.offsetHeight+":"+img.offsetWidth);}</script><input id=inp style="width:400" value="images/logo.gif"><br><button onclick="s()">show</button>

?