[postgis-devel] [PostGIS] #1114: [raster] ST_Resample

[PostGIS]

#1114: [raster] ST_Resample
----------------------------+-----------------------------------------------
 Reporter:  dustymugs       |       Owner:  dustymugs            
     Type:  task            |      Status:  new                  
 Priority:  medium          |   Milestone:  PostGIS Raster Future
Component:  postgis raster  |     Version:  trunk                
 Keywords:                  |  
----------------------------+-----------------------------------------------

Comment(by pracine):

 Replying to [comment:14 dustymugs]:
 > Replying to [comment:12 pracine]:
 > > I don't think so. That would unwisely change the shape of the raster
 footprint. I knew I described this better. It is in the ST_AsRaster()
 specs where I describe how to align the desired raster. I will try to
 describe it better here...
 > >
 > > In the ST_Resample specs, the second series of variant to not define
 what should be the new upperleft corner of the raster. They define a grid
 on which the raster should snap to. So it is neither of your drawings...
 An alignment grid is defined by x, y and a pixelsize. The pixel size can
 be defined with just 'pixelsize', meaning that scalex = scaley and skewx =
 skewy = 0 of with some of those pixelsize parameters (variants 7 and 9).
 This is why I did not call them ulx and uly but just x and y. Those x and
 y are arbitrary upperleft corner of ANY pixel of the new grid to snap to.
 You have to compute the new ulx and uly of the resampled raster
 according/to snap to this grid.
 > >
 > > Sorry if this was not explained...
 >
 > I think I understand what you're describing.  I'm going to have to let
 this sink in for a bit to understand the calculation involved.

 This is basically the same behaviour as ST_SnapToGrid... We should even
 provide a set of alias to the second series of ST_Resample variants named
 SnapToGrid. The first set of variant do not really 'snap to grid'. They
 only change the pixel size without touching the upperleft corner.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1114#comment:16>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.