[postgis-devel] [PostGIS] #1267: [raster] Add manual height/weight support to ST_Resample

[PostGIS]

#1267: [raster] Add manual height/weight support to ST_Resample
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 Reporter:  serveralex      |       Owner:  dustymugs            
     Type:  enhancement     |      Status:  assigned             
 Priority:  medium          |   Milestone:  PostGIS Raster Future
Component:  postgis raster  |     Version:  trunk                
 Keywords:                  |  
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Comment(by bnordgren):

 Replying to [comment:1 dustymugs]:
 >The assumption that you're making about the resulting raster having the
 exact same parameters as the reference raster is incorrect if the two
 rasters are different (such as where the extent of one is larger than that
 of the other).

 Is there a solid justification for this? What does it matter if the
 requested output grid is smaller or larger than the input? All you need to
 do is iterate over every cell in the requested grid and perform the
 resample operation. In any case, the output and input grid definitions
 will never be identical (why resample to the same grid? you already have
 it!)


 Replying to [comment:2 pracine]:
 > You might want to align a raster to another one in which case you need
 to borrow its scales, its skew and its upperleft corner to determine the
 new grid on which to align the new resampled raster. We offer the
 possibility to borrow them from another raster because they are generally
 cumbersome to write by hand. You may also want to explicitly pass those
 parameters.

 I agree. The unit of borrowing should be the entire grid definition
 (width, height, and the affine transform to the geopoint). Note that this
 also requires that the target raster "borrow" the SRID, as the affine
 transform is tied to a particular geospatial CRS.

 However, I don't see why it should be necessary to alter the signature in
 order to do this. The user can construct a raster with no bands, configure
 its grid definition to their heart's content, then require that the
 resampling operation respect the grid definition specified in the "ref"
 raster. If they want to resample many sources to a common grid, they just
 keep specifying the same "ref" raster over and over again.


 > I would prefer the addition of a new signature accepting width and
 height than having one borrowing of dimensions from another raster.

 Again, width and height alone are not useful without all of the other
 contextual information provided in a grid definition. All or nothing! :)

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1267#comment:5>
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