[postgis-devel] [PostGIS] #590: [raster] Implement the two rasters version of ST_MapAlgebra

[PostGIS]

#590: [raster] Implement the two rasters version of ST_MapAlgebra
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 Reporter:  pracine         |       Owner:  jorgearevalo 
     Type:  task            |      Status:  new          
 Priority:  medium          |   Milestone:  PostGIS 2.0.0
Component:  postgis raster  |     Version:  trunk        
 Keywords:                  |  
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 Specs should be added to the wiki soon. Otherwise refer to
 scripts/plpgsql/mapalgebra.sql

 The first version should include optimization provided by the possibility
 to ST_SetValues over an extent (instead of setting one pixel at a time).

 The conditions when to apply such optimizations are still to precise but
 at a first glance you want to set an extent to the values of one of the
 provided raster when the expression the equivalent of 'LAST' and you want
 to set an extent to a single value when there is a replacement value.

 For better optimization we might have to replace the "replacement value"
 concept with four expressions: "NULL-NULL expression", "NULL-value
 expression", "value-NULL expression", "value-value expression". With this
 we could easily identify what is the function involved in non-overlapping
 area and apply the correct optimization. To be followed in the specs...

 The possibility to reference neighbour pixels (to implement focal
 expressions) can be delayed to a further version.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/590>
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