[Mapserver-dev] Rotated Map Rendering

[Daniel Morissette]

Steve Lime wrote:
> 
> Based on your alternatives it seems like 2 mirrors the current meaning
> of an extent. You get that area plus a bit more. This was going to be an
> 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 would 
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 a 
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 extent,
> 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. Probably
> not that big of an issue since only the OGC WMS/WCS specs would leverage
> 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
-- 
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  Daniel Morissette               dmorissette at dmsolutions.ca
  DM Solutions Group              http://www.dmsolutions.ca/
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