Creating Gradients for Web Page Headers with PNG Images - Reintroducing the AlphaImageLoader Microsoft’s proprietary filter
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Before I show you how to build fancy gradients that can be used with certain headers of a given web page, first, I’d like to reintroduce the hands-on example that I developed in the previous article of the series. It was tasked with creating a PNG-based gradient that was tiled horizontally across the whole web document.
The source code corresponding to this practical example looked like this:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Sample web page with PNG-based background (cross-browser version)</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<style type="text/css">
body{
padding: 0;
margin: 0;
}
h1{
padding: 5px;
margin: 0;
font: bold 12px Arial, Helvetica, sans-serif;
color: #000;
}
h2{
padding: 7px 5px 8px 5px;
margin: 0;
background: #fc0;
font: bold 12px Arial, Helvetica, sans-serif;
color: #000;
}
p{
font: normal 12px Arial, Helvetica, sans-serif;
color: #000;
}
#header{
width: 780px;
padding: 10px;
margin-left: auto;
margin-right: auto;
background: #fc0;
}
#navbar{
width: 780px;
padding: 10px;
margin-left: auto;
margin-right: auto;
background: #ffc;
}
#navbar ul{
list-style: none;
}
#navbar li{
display: inline;
padding-right: 4%;
}
#navbar a:link,#navbar a:visited{
font: normal 12px Arial, Helvetica, sans-serif;
color: #039;
text-decoration: none;
}
#navbar a:hover{
text-decoration: underline;
}
#mainwrapper{
clear: both;
width: 800px;
height: 100%;
margin-left: auto;
margin-right: auto;
overflow: hidden;
background: #fff;
}
#mainwrapper .leftcol{
position: relative;
float: left;
}
#mainwrapper .rightcol{
position: relative;
float: right;
}
#leftbar{
width: 180px;
padding: 10px;
}
#centerbar{
float: left;
width: 380px;
padding: 10px;
background: #fff;
}
#rightbar{
width: 180px;
padding: 10px;
}
#footer{
clear: both;
width: 780px;
padding: 10px;
margin-left: auto;
margin-right: auto;
background: #fc0;
}
.contbox{
padding: 10px;
margin-bottom: 10px;
background: #eee;
border: 1px solid #ccc;
}
.gradient{
background: #fff url(bg.png) left top repeat-x;
}
/* use the * html CSS hack to render an alpha-based transparent background */
* html .gradient{
background: #fff;
filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(src='bg.png',
sizingMethod='scale');
}
</style>
</head>
<body class="gradient">
<div id="header">
<h1>This is the header section of the web page</h1>
<p>Contents for header section go here. Contents for header section go here. Contents for header section go here. Contents for header section go here.</p>
</div>
<div id="navbar">
<h1>This is the navigation bar of the web page</h1>
<ul>
<li><a href="#">Link 1</a></li>
<li><a href="#">Link 2</a></li>
<li><a href="#">Link 3</a></li>
<li><a href="#">Link 4</a></li>
<li><a href="#">Link 5</a></li>
<li><a href="#">Link 6</a></li>
</ul>
</div>
<div id="mainwrapper">
<div id="leftbar" class="leftcol">
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
</div>
<div id="centerbar" class="leftcol">
<h2>Section title</h2>
<div class="contbox">
<p>Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here.</p>
<p>Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here.</p>
<p>Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here. Contents for center column go here.</p>
</div>
</div>
<div id="rightbar" class="rightcol">
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
<h2>Section title</h2>
<div class="contbox">
<p>Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here. Contents for left column go here.</p>
</div>
</div>
</div>
<div id="footer">
<h1>This is the footer section of the web page</h1>
<p>Contents for footer section go here. Contents for footer section go here. Contents for footer section go here. Contents for footer section go here. Contents for footer section go here.</p>
</div>
</body>
</html>
As you can see, the above code sample creates a three-column web page that is basically decorated with a gray-colored gradient that fades progressively to transparent by way of a tiny PNG background image, tiled horizontally. Of course, the most important aspect to note with reference to the previous example is the utilization of “AlphaImageLoader,” Microsoft’s proprietary filter within the “gradient” CSS class, to correctly display the PNG graphic when working with IE 6 and below.
If you take a moment and test the above example on both Mozilla Firefox and Internet Explorer, you’ll see that they render this web page gradient as expected. This means that the corresponding “gradient” CSS class really works!
Well, at this point, I assume that building cross-browser web page gradients using the “AlphaImageLoader” filter is a familiar process for you. Thus, taking this into account, it’s time to see how the same approach I followed to create these fancy web document gradients can be applied to certain headers of the document in question.
By extending the use of this approach, you’ll be able to decorate not only the background of a web page, but many other elements of it as well. But, as you may have guessed, this interesting topic will be discussed in detail in the following section. So, jump ahead and read the next few lines. I’ll be there, waiting for you.
Next: Decorating headers of a web page >>
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