[mapserver-dev] WMS exception for requests width height=1

[Lime, Steve D (MNIT)]

Patch seems reasonable IMHO... --Steve

From: mapserver-dev-bounces at lists.osgeo.org [mailto:mapserver-dev-bounces at lists.osgeo.org] On Behalf Of Martin Kofahl
Sent: Wednesday, April 10, 2013 3:04 PM
To: Worth Lutz
Cc: MapServer Dev Mailing List
Subject: Re: [mapserver-dev] WMS exception for requests width height=1

In that case the, MapServer should calculate with the distance from the size from the center of a single pixel to border, I think. So 0.5. Changes in https://github.com/mapserver/mapserver/pull/4629

2013/4/10 Worth Lutz <wal3 at mindspring.com<mailto:wal3 at mindspring.com>>
If I understand correctly, it is because MapServer is based upon a cell size of center of pixel to center of pixel.

With 1 pixel you have nothing. With 2 pixels you have 1 cell.

Worth Lutz
________________________________
From: mapserver-dev-bounces at lists.osgeo.org<mailto:mapserver-dev-bounces at lists.osgeo.org> [mailto:mapserver-dev-bounces at lists.osgeo.org<mailto:mapserver-dev-bounces at lists.osgeo.org>] On Behalf Of Martin Kofahl
Sent: Wednesday, April 10, 2013 2:40 PM
To: MapServer Dev Mailing List
Subject: [mapserver-dev] WMS exception for requests width height=1

Hello,
currently, I see wms clients (qgis, arcgis 10) doing getmap requests with height=1. MapServer (6.2) throws an exception:

msDrawMap(): Image handling error. Unable to initialize image.
msCalculateScale(): General error message. Invalid image extent, minx=nan, miny=nan, maxx=nan, maxy=nan.

The reason is in msAdjustExtent(), where the cell size is calculated using MS_CELLSIZE(miny,maxy,height), defined as ((max - min)/(d-1)). Formally, I don't see any reasons against 1 pixel requests. What are the reasons for "d-1"?

Martin
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