[Mapserver-dev] Rotated Map Rendering

[Frank Warmerdam]

Julien-Samuel Lacroix wrote:
> Frank, a question or two about this. I know I'm late, but I'll trow my 
> idea in anyway, feel free to ignore them. Is there any advantage of 
> using the x/y min/max + rotation datastructure? What was the main reason 
> of going this way?
 >
> Because my thought was since an extent defined this way with angle 0 
> will be the same thing as a regular extent, we could maybe support both 
> extent definition and put, like it have been suggested many time, the 
> rotation angle in a separate keyword.

Julien,

I think what you are suggesting is what has actually been done.  As things
stand in my local 4.3 tree the we have definitions like:

typedef struct {
  int  need_geotransform;

  double rotation_angle;

  double geotransform[6];    // Pixel/line to georef.
  double invgeotransform[6]; // georef to pixel/line
} geotransformObj;

typedef struct {
  ...
   int height, width;
   rectObj extent; /* map extent array */
   double cellsize; /* in map units */
   geotransformObj gt; /* rotation / geotransform */
   ...
} mapObj;

So, the geotransformObj now carries the rotation but the extent
information is just in the normal extent rectObj.

In the mapfile I am just using the ANGLE keyword to set the
gt.rotation_angle.

eg.

SIZE 300 400
EXTENT 360015 4359225 371025 4373355
ANGLE 30

 > I don't know how much effort it
> will be hard integrate, but this could keep your original plan on the 
> track and lead to future enhancement that will take advantage of this 
> definition (like camera model features).

I'm not sure how this helps to address camera models or other advanced
features.

> Ishh! Round map!
> Just kidding!

Yikes!  Frightening thought ... well perhaps with some sort of masking.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent