[postgis-devel] [PostGIS] #1648: [raster] ST_AsRaster unexpected result

[PostGIS]

#1648: [raster] ST_AsRaster unexpected result
-----------------------+----------------------------------------------------
  Reporter:  jomarlla  |       Owner:  dustymugs    
      Type:  defect    |      Status:  closed       
  Priority:  medium    |   Milestone:  PostGIS 2.0.1
 Component:  raster    |     Version:  trunk        
Resolution:  wontfix   |    Keywords:               
-----------------------+----------------------------------------------------
Changes (by dustymugs):

  * status:  assigned => closed
  * resolution:  => wontfix


Comment:

 After doing some additional digging, the difference in burned pixels
 boiled down to the use of the "touched" parameter.

 Having "touched" be true causes the difference of burned pixels (42 vs 40
 on 64 vs 32-bit)...

 {{{
 SELECT
         ST_Count(
                 ST_AsRaster(
                         'POLYGON ((11 11, 21 11, 26 21, 16 21, 11
 11))'::geometry,
                         1.5::double precision, 2::double precision,
                         11, 11,
                         '8BUI',
                         100, 0,
                         0, 0,
                         true
                 )
         );
 }}}

 With "touched" being false, 32 and 64-bit Linux return the same number of
 burned pixels: 34.

 {{{
 SELECT
         ST_Count(
                 ST_AsRaster(
                         'POLYGON ((11 11, 21 11, 26 21, 16 21, 11
 11))'::geometry,
                         1.5::double precision, 2::double precision,
                         11, 11,
                         '8BUI',
                         100, 0,
                         0, 0,
                         false
                 )
         );
 }}}

 Since everything is the same except the "touched" parameter, which only
 sets the ALL_TOUCHED option flag when calling GDALRasterizeGeometries(),
 there is a behavior difference in GDAL's algorithm.

 I'm closing this ticket as there is nothing that can be done on the
 PostGIS side.  Might be worth submitting a new ticket to GDAL though
 highlighting the difference in behavior for ALL_TOUCHED in 32 vs 64-bit
 environments.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1648#comment:11>
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.