MSIE PNG Alpha Transparency

In usual form, MSIE doesn’t directly implement Alpha-Transparency on PNG images. Typically this feature is used to allow for anti-aliased gradients on images so that they can be used to support a variety of backgrounds.

There are a variety of solutions online for this problem, however I take issue with most, here’s why:

  • .htc files – this is a proprietary Microsoft solution, to add support on most web servers the MIME type must also be added.
  • filter: progid: – this too is utilizing a standard in Microsoft’s own particular way.

While neither of these is perfect, the ‘filter:’ is obviously the best of two evils. Surround it with the “Conditional If” comments (previously documented) and you’re at least safe for most other browsers.

Here’s my example code:

<!–[if gte IE 5.5000]>
<script type=”text/javascript”>
function correctPNG() // correctly handle PNG 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 = ( ? “id='” + + “‘ ” : “”;
var imgClass = (img.className) ? “class='” + img.className + “‘ ” : “”;
var imgTitle = (img.title) ? “title='” + img.title + “‘ ” : “title='” + img.alt + “‘ “;
var imgStyle = “display:inline-block;” +;
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;
window.attachEvent(“onload”, correctPNG);


Good luck out there!

Open Source Diffs/Compare Tools

I often find it necessary to compare separate branches of large programming projects in Java/JSP and PHP. Comparing single files manually proves to be very time consuming. I’ve found that software to do the recursive comparisons makes this much easier as it greatly reduces the effort.

Personally, I’m currently fond of WinMerge (on Windows platforms), though I’ve got a lot of peers that swear by Beyond Compare. Regardless their usage is very similar.


Beyond Compare: