图片移动放大和缩小怎么代码怎么写呀?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<SCRIPT LANGUAGE="JavaScript">
<!--
function zoomIn() {
document.all["imgt"].width=100;
document.all["imgt"].height=100;
}
function zoomOut() {
document.all["imgt"].width=10;
document.all["imgt"].height=10;
}
function rePosition() {
document.all["imgt"].style.position = "relative";
document.all["imgt"].style.top = 100;
document.all["imgt"].style.left = 100;
}
//-->
</SCRIPT>
</HEAD><BODY>
<img src="abc.jpg" width=50 height = 50 id= "imgt">
<input type=button onclick="zoomIn()" value="zoom in">
<input type=button onclick="zoomOut()" value="zoom out">
<input type=button onclick="rePosition()" value="rePosition">
</BODY>
</HTML>