透明的box背景

2015/02/03 41721
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
        "http://www.w3.org/TR/REC-html40/transitional.dtd">
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" >
<style type="text/css">
body {
     background: url(./water_lilies.jpg);
     background-repeat: no-repeat;
}

/*This is where the magic happens!*/
div.box {
     /*Any properties you'd want the box to have.*/
     /*Would probably be position, dimension type stuff.*/
     /*Though personally I would have a div outside this
       to control the dimensions.*/
     border: 1px solid #000000;
     position: relative;
     width: 100%;
}
div.box_contents {
     background-color:transparent;
     height: 100%;
     position: relative;
     width: 100%;
     z-index: 101;
}
div.box_background {
     background-color: white;
     height: 100%;
     filter:alpha(opacity=75); /* IE's opacity*/
     left: 0px;
     opacity: 0.75;
     position: absolute;
     top: 0px;
     width: 100%;
     z-index: 99;
}
</style>
 
<script type="text/javascript">
function change_w(id, pixels) {
     var x = document.getElementById(id);
     x.style.width = x.offsetWidth + pixels + "px";
}
function change_h(id, pixels) {
     var x = document.getElementById(id);
     x.style.height = x.offsetHeight + pixels + "px";
}

/*This function is meant to be used when you are needing
faux getElementsByName() in IE. IE seems so use the 'id'
attribute instead of 'name' when you use getElementsByName().

tag = This tag name that the 'name' attribute you want to 
      get is attached to. Like if you called getElementsByTagName().
      
name = The value of the 'name' attribute you want.
*/
function getElementsByName_iefix(tag, name) {
     var elem = document.getElementsByTagName(tag);
     var arr = new Array();
     for(i = 0, iarr = 0; i < elem.length; i++) {
          att = elem[i].getAttribute("name");
          if(att == name) {
               arr[iarr] = elem[i];
               iarr++;
          }
     }
     return arr;
}

/*This function resets the height and width of the background
to that of it's parent element's height and width.

tbg_id = This is the value of the name attribute you named all your
         backgrounds.
*/
function transparentbg(tbg_id) {
     var bak = getElementsByName_iefix("div", tbg_id);
     for(i = 0; i < bak.length; i++) {
          bak[i].style.height = bak[i].parentNode.clientHeight + "px";
          bak[i].style.width  = bak[i].parentNode.clientWidth + "px";
     }
}
</script>
</head>
<body onload="transparentbg('bg_name')" onclick="transparentbg('bg_name')">
<div style="width: 500px;">
     
     
     <div class="box" id="box">
          <div class="box_background" name="bg_name"> </div>
          <div class="box_contents">
               Width: <input type="button" value="+" onclick="change_w('box', 30);" /> / <input type="button" value="-" onClick="change_w('box', -30);" /><br />
               Height: <input type="button" value="+" onclick="change_h('box', 30);" /> / <input type="button" value="-" onClick="change_h('box', -30);" /><br />
               <!-- This is a fix that is mainly for IE. Otherwise you'll get white space where you don't want it.-->
               <div style="padding: 2px; font-weight: bolder; font-size: 14px;">
                    This is the box contents! :O <br />
                    You see, the background will cover the whole div block no matter how wide or tall!
                    <br />
                    <br />
                    <br />
                    Look at me! More content!
               </div>
          </div>
     </div>
</div>
</body>
</html>
代码片段
