[Mapserver-users] WMS server image black padding and aspect ratio

[Ed McNierney]

Eric -

You may be slightly misunderstanding the WMS problem.  The WMS
specification states that if an image request specifies an OUTPUT image
size (WIDTH= and HEIGHT=) and a geographic bounding box (BBOX=) that are
not consistent with one another (for example, WIDTH=200,HEIGHT=100 and
BBOX=0,0,100,100, so a 100x100 area is being requested in a 200x100
image) that the 100x100 geographic area be stretched in the X direction
so it's 200 pixels wide.  MapServer does not do this, but instead
renders a 200x100 geographic area to fill the box without stretching the
OUTPUT image.

Your comment makes it sound like you have INPUT images with different X
and Y resolutions/scales.  This is completely unrelated to the problem
with the WMS interface, and MapServer can handle those images with no
problems - assuming of course that the metadata correctly describes the
input images.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242 

-----Original Message-----
From: Eric Sokolowsky [mailto:eric.sokolowsky at gsfc.nasa.gov] 
Sent: Wednesday, January 28, 2004 2:29 PM
To: Daniel Morissette
Cc: mapserver-users at lists.gis.umn.edu
Subject: Re: [Mapserver-users] WMS server image black padding and aspect
ratio

On Fri, 23 Jan 2004, Daniel Morissette wrote:

> Eric Sokolowsky wrote:
> > I am running mapserver 4.0.1 but this aspect also appears with the 
> > version in CVS.  I am using mapserver as a WMS server on a Red Hat 
> > Linux 9 system.  When I request an image that is not the same aspect

> > ratio as the original image on the server, it seems that the image I

> > get is not stretched so that it fills the entire frame.  The aspect 
> > ratio of the original source is maintained and black bars either 
> > appear above and below or else on both sides, similar to the effect 
> > of watching widescreen movies on a regular TV.  Is this the intended

> > behavior, and if so, is there a way to turn it off?
> > 
> 
> The short answer is that MapServer doesn't support rendering maps with

> different X and Y scales.  This is one of the only issues with 
> MapServer before it passes all the OGC WMS tests.

This is most unfortunate.  It is absolutely critical for my application
to allow this.  Most of the images that I want to serve have different X
and Y scales, and it would be very difficult to rescale all of them.
Also, even if I rescaled all of the images, it would not solve the
problem of requesting a different aspect ratio bounding box.

Is there work being done to fix this problem?  I am willing to jump into
the code to try and find a way to solve it, but I am not familiar with
the code and it may take me a while to get up to speed with it.

> For the long story, see the following thread in the archives:
> http://mapserver.gis.umn.edu/data2/wilma/mapserver-users/0401/msg00105
> .html
> 
> Daniel
> 

-- 
    ____   __     Eric Sokolowsky    (GST)  NASA Goddard Space Flight
Center 
   / __/__/_/__  Visualization Programmer    Scientific Visualization
Studio
  / __/ _/ / _/ 301.286.3751                  Mailstop 935.0 Bldg 28 Rm
E102
 /___/_//_/__/ eric.sokolowsky at gsfc.nasa.gov   Greenbelt, MD 20771

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