[postgis-tickets] [PostGIS] #2341: [raster] ST_MapAlgebra mask parameter

[PostGIS]

#2341: [raster] ST_MapAlgebra  mask parameter
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 Reporter:  nclay        |       Owner:  dustymugs    
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.2.0
Component:  raster       |     Version:  trunk        
 Keywords:               |  
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Comment(by nclay):

 Nulls?

 How should we handle null as a double can not be null in c? In my current
 code I treat 0 as null for a non-weighted mask, and ignore the possibility
 for a null in a weighted mask.

 {{{
              if ( mask == NULL ) {
                   values[_y][_x] = npixel[i].value;
                   nodatas[_y][_x] = 0;
                 }else{
                   if( !weighted ){
                     if( mask[_y][_x] == 0 ){
                       values[_y][_x] = 0;
                       nodatas[_y][_x] = 1;
                     }else{
                       values[_y][_x] = npixel[i].value;
                       nodatas[_y][_x] = 0;
                     }
                   }else{
                     values[_y][_x] = npixel[i].value * mask[_y][_x];
                     nodatas[_y][_x] = 0;
                   }
                 }

 }}}

 What value should be treated as a NULL in the case of a weighted mask? I
 am thinking 0, but I want some thought on this or should we have a mask
 nodata array?

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2341#comment:11>
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