[Tilecache] TileCache Transparent Overlays. Is it possible?

[Christopher Schmidt]

On Fri, Mar 30, 2007 at 01:57:43PM +0800, Rupert de Guzman Jr wrote:
> Hi Everyone,
> 
> Really appreciate all the replies...
> Then I tried appending "transparent=true" to tilecache.cfg based on Eric's
> suggestion...
> That worked. Now I wonder why... Nevertheless, its working now. Again many
> thanks
> to everyone...

TileCache pays almost no attention to the URL: Only the BBOX and the
layername matter. Anything else is simply ignored: so your transparency
being set in OpenLayers actually has 0 affect.

The reason for this is that TileCache can only store one copy of an
image. If the URL parameters modified the content, you could get an
inconsistent cache.

This is 'by design', insofar as there is no obvious solution (other than
to complain more loudly when TC Gets parameters it isn't expecting,
which is an outstanding FIXME in the code). The lack of error message is
not by design, and I'm sorry you got bit by the poorly documented
behavior. 

Regards,
-- 
Christopher Schmidt
MetaCarta