javascript 实现图片放大缩小

<script language="javascript">
 var mm=1;
 function imgzoom(h)
 {  
  if (h==1)
  {
  mm+=0.2;
  mm=Math.min(2,mm);
  document.all.imgjpg.style.zoom=mm;
  //alert(mm*100+"%");
  }
  else if(h==2)
  {
  mm-=0.2;
  mm =Math.max(0.05, mm);
  //alert(mm*100+"%");
  document.all.imgjpg.style.zoom=mm;
  }
 }
</script>
<input type=button value="放大" onclick="imgzoom(1);">
<input type=button value="缩小" onclick="imgzoom(2);">

<IMG id="imgjpg" name="imgjpg" src="images/liyan998_05.gif" width="121" height="22">