[postgis-devel] [PostGIS] #1525: [raster] Redefine and expand the keywords available to MapAlgebra expressions

[PostGIS]

#1525: [raster] Redefine and expand the keywords available to MapAlgebra
expressions
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 Reporter:  dustymugs    |       Owner:  pracine      
     Type:  enhancement  |      Status:  new          
 Priority:  critical     |   Milestone:  PostGIS 2.0.0
Component:  raster       |     Version:  2.0.x        
 Keywords:               |  
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Comment(by strk):

 One idea could be prefixing with : That character is used by psql for
 expanding variables. Example:

 echo "select :n" | psql --set n="'hello'"

 So we would have:

 * :rast * :rast1 * :rast2

 Then I'd see those as roots for further detail, "rast" would identify the
 pixel taken in consideration, and you could then get more informations
 about it by adding a point and another label:

  * :rast.val
  * :rast.x
  * :rast.y

 Or the shorter and more underground:

  * :r.v :r.x :r.y
  * :r1.v :r1.x :r1.y
  * :r2.v :r2.x :r2.y

 Note that X and Y don't make things much slower (except in the keyword
 substitution phase, which can be optimized further). I also think all the
 other informations can be derived with a proper expression.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1525#comment:8>
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