[OpenLayers-Dev] PNG Transparency on IE 6

[Christopher Schmidt]

On Fri, Mar 02, 2007 at 10:29:57AM +0100, Steven M. Ottens wrote:
> Hi antonio,
> 
> There is a solution; the FixPNG workaround, but it's slow. This is  
> not a big problem if you have 3 PNG images, but if you enable tiling,  
> you easily get up to 30 images and it takes up to minutes to draw the  
> layers. Also with this workaround the images are not displayed until  
> all the images are loaded and fixed. Which gives your application a  
> very sluggish feel to it.

Indeed, we used to have this on by default, but turned it off when we
realized that it basically made applications unusable.

The way to enable this is to add an 'alpha':true option to your layer
options:

 new OpenLayers.Layer.WMS("Name", "url", {'params':'here'},
 {'alpha':true});

But you should be aware that this is likely to cause serious slowdowns
in IE6, and should be tested before deployment.

I recommend using GIF (or 8bit PNGs) for your overlays in IE6.  

Regards,
-- 
Christopher Schmidt
MetaCarta