[mapserver-users] GDAL WMS

[James Perrins]

Hi,

I've been trying to use this:
http://www.gdal.org/frmt_wms.html

I've tried both with a tile server - and with a WMS service (as it
seemed like an easy way to get caching)
It basically works, but I have problems with the quality of the image
that mapserver produces

It seems that mapserver requests too many tiles / images from WMS for
the current screen image required - it then re-samples this resulting
in poor quality being served through mapserver (and often with too
much detail for the size returned meaning its still more broken up on
labels etc)

The images from the WMS / tile server (and stored in the cache) are
fine - so its definitely mapserver / GDAL minidriver thats causing the
problem.

Also - with the WMS call - what are SizeX and SizeY about - altering
these can effect the quality of the image - its almost as if this is
the image size that the WMS would be if served out as one massive
image as the most details scale ??  I don't really see why they are
needed?



example for WMS:

<GDAL_WMS>
    <Service name="WMS">
	<Version>1.1.1</Version>
	<ServerUrl>http://localhost/scripts/mapserv.exe?map=D:\My.map&</ServerUrl>
	<SRS>EPSG:27700</SRS>
        <ImageFormat>image/png</ImageFormat>
        <Layers>TOPOLINE,TOPOAREA</Layers>
        <Styles></Styles>
    </Service>
    <DataWindow>
        <UpperLeftX>300965</UpperLeftX>
        <UpperLeftY>236781</UpperLeftY>
        <LowerRightX>323072</LowerRightX>
        <LowerRightY>216968</LowerRightY>
        <SizeX>1115800</SizeX>
        <SizeY>1000000</SizeY>
    </DataWindow>

    <BlockSizeX>512</BlockSizeX>
    <BlockSizeY>512</BlockSizeY>
    <Projection>EPSG:27700</Projection>
</GDAL_WMS>

Many Thanks
James