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semitransparent background 3

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davikokar

davikokar

Technical User
May 13, 2004
523
IT
hallo,
do you know if it possible to have a semitransparent bakground? I tried with many image formats but none would work (gif, bmp, jpg, png). Maybe there is another way.
thanks
 
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You can put an image into the background of a DIV and then set some transparency filter on the DIV. The end result is about the best you are going to achieve (although it will not be totally cross-browser).

Jeff

 
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If "it" is a background, then what's behind it that you will see when it's semi transparent?

If you mean that you wish to make a page element semi transparent then it is possible to apply opacity to elements using CSS and MS filters. Not sure how well it's supported but try this.

Code: 
<?xml version="1.0" encoding="iso-8859-1"?>
<!doctype html public "-//W3C//DTD XHTML 1.0 Transitional//EN" "[URL unfurl="true"]http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">[/URL]
<html xmlns="[URL unfurl="true"]http://www.w3.org/1999/xhtml">[/URL]
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

 <style type="text/css">
	body {
	 background-color:#f00;
	}
	
	.trans {
		opacity:0.85;				
		filter:alpha(opacity=85);
	}
 </style>
</head>

<body>
	<img src="wheel.gif"  alt="put an image here, no transparency" />
	<img src="wheel.gif" class="trans" alt="put the same image here" />
</body>
</html>

The above works in FF and IE6 under Windows


Foamcow Heavy Industries - Web design and ranting
Target Marketing Communications - Advertising, Direct Marketing and Public Relations
I wonder what possesses people to make those animated gifs. Do you just get up in the morning and think, "You know what web design r
 
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You could use a PNG format image, which supports alpha levels... although this would only work in supported browsers (which doesn't incvlude IE6, even though IE/Mac does!).

That, or using CSS for opacity (as both Jeff and Pete have suggested).

Hope this helps,
Dan



[tt]Dan's Page [blue]@[/blue] Code Couch
[/tt]
 
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thanks to all. I tried with the png but it doesn't work (I'm working with IE6/windows: isn'it the most common browser?). But the opacity filters works: I didn't know about it. Is it part of CSS2 definitions?
 
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IE6 for Windows supports 8 bit png's with a transparency, but as you point out this allows only for "on" or "off" transparency and not various levels thereof.

If you are only concerned with what some may term decent browsers, then a 24 bit png with and alpha transparency will look lovely.

Foamcow Heavy Industries - Web design and ranting
Target Marketing Communications - Advertising, Direct Marketing and Public Relations
I wonder what possesses people to make those animated gifs. Do you just get up in the morning and think, "You know what web design r
 
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Also note that with 4 lines of CSS, you can get opacity working in most of the common modern browsers: Firefox, Netscape 6+, IE5+, and Safari, as well as any browser that supports the opacity style.

Don't just settle for IE, unless you know your target browser audience.

Dan



[tt]Dan's Page [blue]@[/blue] Code Couch
[/tt]
 
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Dear Karerda,

I supply you with a MS-Explorer PNG hack.
The hack consists of two javascript functions which you will be able to use both or seperated to suit your needs.


This goes in the header of the HTML
Code: 
<!--[if IE]>
<script language="JavaScript" src="/js/PngIeHack.js" type="text/JavaScript">
</script>
<![endif]-->

Save code below as /js/PngIeHack.js

Code: 
	window.attachEvent("onload", correctPNG);
	window.attachEvent("onload", alphaBackgrounds);

function correctPNG() // correctly handle PNG "IMG Element" transparency in Win IE 5.5 or higher.
   {
   for(var i=0; i<document.images.length; i++)
      {
	  var img = document.images[i]
	  var imgName = img.src.toUpperCase()
	  if (imgName.substring(imgName.length-3, imgName.length) == "PNG")
	     {
		 var imgID = (img.id) ? "id='" + img.id + "' " : ""
		 var imgClass = (img.className) ? "class='" + img.className + "' " : ""
		 var imgTitle = (img.title) ? "title='" + img.title + "' " : "title='" + img.alt + "' "
		 var imgStyle = "display:inline-block;" + img.style.cssText
		 if (img.align == "left") imgStyle = "float:left;" + imgStyle
		 if (img.align == "right") imgStyle = "float:right;" + imgStyle
		 if (img.parentElement.href) imgStyle = "cursor:hand;" + imgStyle
		 var strNewHTML = "<span " + imgID + imgClass + imgTitle
		 + " style=\"" + "width:" + img.width + "px; height:" + img.height + "px;" + imgStyle + ";"
	     + "filter:progid:DXImageTransform.Microsoft.AlphaImageLoader"
		 + "(src=\'" + img.src + "\', sizingMethod='scale');\"></span>"
		 img.outerHTML = strNewHTML
		 i = i-1
	     }
      }
   }

function alphaBackgrounds() // correctly handle PNG "BACKGROUNDCOLOUR" transparency in Win IE 5.5 or higher.
{
	var rslt = navigator.appVersion.match(/MSIE (\d+\.\d+)/, '');
	var itsAllGood = (rslt != null && Number(rslt[1]) >= 5.5);
	for (i=0; i<document.all.length; i++){
		var bg = document.all[i].currentStyle.backgroundImage;
		if (itsAllGood && bg){
			if (bg.match(/\.png/i) != null){
				var mypng = bg.substring(5,bg.length-2);
				document.all[i].style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='"+mypng+"', sizingMethod='scale')";
				document.all[i].style.backgroundImage = "url('images/1pixel.gif')";
			}
		}
	}
}

For a working example see this website is currently under construction but it has transparant PNG in the CSS(2) background.

uses the other function because it has transparant icons on top of the navigation background.

If you experience any difficulties, please let me know.

Kind Regards,
Jeroen Haan


HAAN.net, E-Business & Multimedia Solutions, website design, e-commerce,
portal development
 
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