[mapserver-users] Cascading WMS

[Daniel Morissette]

Jerry O'Sullivan wrote:
> 
> I have set up Mapserver to read a WMS server and then feed this out via 
> WMS. The image quality is degraded by MapServer so it is re rendering 
> the image.
> 
> How can I get MapServer to simply pass the image that it gets from the 
> WMS server on instead of re rendering?
> 

I can think of two reasons for loss of image quality in cascaded WMS layers:

1- Incompatible output format. For instance, if the cascaded WMS returns 
  24 bit imagery (PNG24 or JPEG) and your MapServer is configured for 8 
bits output (GIF, PNG8) then you will experience some color issues.

2- Reprojection. Make sure the SRS that is used by the WMS client is 
supported by the cascaded server and listed in the wms_srs metadata. 
Reprojection of the cascaded WMS request (required if the requested SRS 
is not listed as being supported by the remote server) can greatly 
degrade image quality. If your client calls MapServer with a SRS that is 
supported by the remote WMS server then it should make essentially the 
same request to the remote server and there should be no transformation 
or quality loss.

HTH

Daniel
-- 
Daniel Morissette
http://www.mapgears.com/