[postgis-devel] [PostGIS] #1536: [raster] There should be an option for setting the nodata value in certain variants of ST_Intersection(raster, raster) (was: [raster] There should be an option for certain variants of ST_Intersection(raster, raster))

[PostGIS]

#1536: [raster] There should be an option for setting the nodata value in certain
variants of ST_Intersection(raster, raster)
---------------------+------------------------------------------------------
 Reporter:  pracine  |       Owner:  pracine      
     Type:  defect   |      Status:  new          
 Priority:  low      |   Milestone:  PostGIS 2.0.0
Component:  raster   |     Version:  trunk        
 Keywords:           |  
---------------------+------------------------------------------------------

Comment(by pracine):

 Also: At first I was thinking that those nodata value parameters should be
 used only when the requested band do not have a nodata value defined but I
 think this will become confusing.

 I think in the absence of such an argument, if the raster do not have a
 nodata value defined the ST_MinPossibleValue() should be used.

 If the argument is provided and the provided raster DO have a nodata value
 defined then the provided value should replace the nodata value of the
 raster (actually it does not replace it as we have to produce a new raster
 anyway).

 You can achieve this by passing the provided nodata value as the alternate
 expressions. Here is an example I use in ST_Tile():

 ST_SetBandNodataValue(ST_MapAlgebraExpr(rast, 1, geomrast, 1, 'RAST1',
 newpixtype, 'SECOND', newnodata::text, newnodata::text, newnodata),
 newnodata);

 As I said previously it is the responsability of the caller of
 ST_MapAlgebraExpr() to determine and set the new nodata value and the new
 pixel type.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1536#comment:18>
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.