[Mapserver-dev] Rotated Map Rendering

Steve Lime steve.lime at dnr.state.mn.us
Thu May 20 13:27:41 EDT 2004

Will people really be moving between rotated and non rotated worlds? The
important question is will angles change throughout the course of
interacting with
an app. If so then thats a strong argument for 1. If angles are fixed
then I still like
2, since at least scale would be constant from map to map. I suppose
max flexibilty
suggests not doing that though.



>>> Daniel Morissette <dmorissette at dmsolutions.ca> 5/20/2004 10:51:41
AM >>>
Steve Lime wrote:
> Based on your alternatives it seems like 2 mirrors the current
> of an extent. You get that area plus a bit more. This was going to be
> issue regardless of how you define your AOI. What was your original
> plan?

The drawback of #2 is that it is not possible to predict the actual 
scale of the map without complicated calculations, and I fear that some

apps would be broken by this additional adjustment of extents that
be done to accomodate the rotation.

OTOH, if we went with #1, an app could continue to work with the 
"extents before rotation" and completely ignore the fact that there is
rotation, as long as it calls the pixel2georef()/georef2pix() functions

when it deals with user inputs.

> I thought that to deal with the non-square pixel issue in the future
> we'd probably have to set a flag that would alter the meaning of
> that is, you'd get extactly that extent albeit stretched a bit if
> necessary. I'm not sure how that would play out with rotation.
> not that big of an issue since only the OGC WMS/WCS specs would
> that capability very often.

I like the idea of doing this by adding a new parameter (flag) to tell

MapServer that the extents shouldn't be adjusted to the width/height 
aspect ratio. Maybe something like "FORCEEXTENTS TRUE/FALSE" with a 
default to FALSE that maintains the current behavior? (I'm sure we can

find a better nanme for the keyword)

  Daniel Morissette               dmorissette at dmsolutions.ca 
  DM Solutions Group              http://www.dmsolutions.ca/ 

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