长度和宽度自动缩放

高度自动
height:expression(document.180.clientWidth < 180? "180px": "auto" );

宽度限制
 class="imgzoom"
.imgzoom img {behavior: url("${base}/styles/imgzoom.htc");
<script language="javascript">
  var _width = element.width;
  var _hieght = element.height;
  var _maxpixel = _width;
  var _which = "w";
  var maxwidth = 680;
  var maxheight = 680;
 
  //element.onmousewheel = test;
  if (element.width > maxwidth) {
    element.width = maxwidth;
    element.removeAttribute("height");
   
    if (element.parentElement.tagName != "A"){   
      var _html = "";
      _html += "<a href=\""+element.src+"\" target=\"_blank\">";
      _html += element.outerHTML;
      _html += "</a>";
      element.outerHTML = _html;
    }
  }
  /*
  if (height > _width) {
    _maxpixel = _hieght;
    _which = "h";
  }
  if (_which == "w") {
    if (element.width > maxwidth) {
      element.width = maxwidth;
      element.removeAttribute("height");
    }
  }
  else {
    if (element.height > maxheight) {
      element.height = maxheight;
      element.removeAttribute("width");
    }
  }*/

  function test() {
    return zoomimg(element)
  }

function zoomimg(pic){
  var zoom=parseInt(pic.style.zoom,10)||100;
  zoom+=event.wheelDelta/12;
  if (zoom>0) pic.style.zoom=zoom+'%';
  return false;
}
</script>