[OpenLayers-Users] layers not transparent [sum]

[Richard Greenwood]

My MapServer layers were not transparent - they entirely masked each
other out. The problem had nothing to do with OpenLayers. In the
MapServer map file, one needs to set:
   TRANSPARENT ON
or it can be passed to MapServer as 'map_transparent':'ON'

You may also need: {"isBaseLayer":false}

In typical MapServer applications, all of the requested layers are
combined into a single image on the server and that image is delivered
to the client (browser), so transparency is not usually a
consideration. With OpenLayers, each layer is delivered to the client
as a separate image, and OpenLayers combines them. Hence the need for
transparency.

Thanks for help from Christian, Brad, Christopher, and Arnd,
Best regards,
Rich

-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com