Raya Deleva’s Web
/ Web development
The PNG problem in Windows Internet Explorer
For the Web, PNG really has three main advantages over GIF:
- alpha channels (variable transparency),
- cross-platform gamma correction (control of image brightness) and color correction
- two-dimensional interlacing (a method of progressive display).
PNG also compresses better than GIF in almost every case (5% to 25% in typical cases).
Here is a JavaScript-based PNG fix for Internet Explorer 5.5 and 6 on Windows. The fix allows IE to properly render PNG alpha transparency.
<!--[if lt IE 7]>
<script language="JavaScript">
function correctPNG() // correctly handle PNG transparency in Win IE 5.5 & 6.
{
var arVersion = navigator.appVersion.split("MSIE")
var version = parseFloat(arVersion[1])
if ((version >= 5.5) && (document.body.filters))
{
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
}
}
}
}
window.attachEvent("onload", correctPNG);
</script>
<![endif]-->
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category: Web development, posted date: 28.06.2006, Comment
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