[postgis-devel] [raster] Implementations of rotation and pixel size.

David Zwarg dzwarg+postgis at azavea.com
Thu Aug 18 14:36:31 PDT 2011

Greetings raster devs,

I took a day to implement the outstanding tickets that I had for some of the
accessors related to rotated rasters:

   - #928 - Implement ST_PixelWidth
   - #929 - Implement ST_PixelHeight
   - #936 - Implement ST_Rotation
   - #482 - Implement ST_SetRotation<http://trac.osgeo.org/postgis/ticket/482>

If someone could take a moment to review the patches attached to those
tickets, that would be helpful. One of the things that I did not do was to
limit the rotation amount in ST_SetRotation. I was reading more on the world
file, and it sounds like a raster shouldn't be rotated more than 90 degrees
-- should that be a hard limit in ST_Rotation?  If the rotation exceeds 90
degrees, does the affine transformation go haywire? In addition, the
UpperLeft position should realistically be changed. Otherwise, you could
technically define different rasters that cover the same area, but with
different UpperLeft coordinates (imagine if the geotransform put the
UpperLeft pixel at the lower right, and applied a 180 degree rotation).

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