Summary: Steps for displaying PNG images with 8bit alpha transparency
Version: 0.1 18 Mar 2006
Prerequisites: None
Status: Limited testing
Maintainer: zkarj
Categories: Images

Questions answered by this recipe

  • How can I make Internet Explorer (on Windows) display transparency properly?


Add the following lines to local/config.php

if ((strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE') !== FALSE) &&
    (strpos($_SERVER['HTTP_USER_AGENT'], 'Mac_')  == FALSE))
   { $UseAlphaFilter = 1; } else { $UseAlphaFilter = 0; }

This allows for detecting the IE browsers that cannot cope natively with 8bit transparency.

Use the following markup to include the image.

(:if !enabled UseAlphaFilter:)
(:if enabled UseAlphaFilter:)
(:div id='png1' style='[=width:300px; height:200px; padding:0px; filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src="", sizingMethod="image")=]':)

Elements that you will need to change to suit your own situation are:

  • The name of the image (trans.png above) on the Attach: and in the URL.
  • The width= and height= values should match your image dimensions.
  • The main part of the URL will need to reflect your site and the location of the image. In this case, the example page is in the Main group.


  • Tested with Firefox 1.5 and IE 6.0 on Windows XP SP2.
  • I have tested this only with a start-of-line unfloated image. It may be possible to add additional markup to allow floating (on both Attach: and (:div:)).
  • There may be a better way to specify the URL - i.e. in relative form and maybe using variables to automatically locate the correct folder.

Release Notes

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See Also



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