Changes between Version 132 and Version 133 of WKTRaster/SpecificationWorking03


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Timestamp:
Jul 8, 2011, 8:55:48 AM (13 years ago)
Author:
pracine
Comment:

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  • WKTRaster/SpecificationWorking03

    v132 v133  
    228228'''Details for 5) to 8) Two rasters versions'''
    229229
    230  * A simple PL/pgSQL prototype exists in http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql/st_mapalgebra.sql. This version iterates over every pixel of the unionized extent of two rasters even if there are large areas where both rasters are absent and hence are interpreted as nodata values. An optimized prototype, trying to set those large nodata areas as well as areas where only one raster is present (this is the case when unioning two contiguous non-overlapping rasters) as a block (not pixel by pixel) using ST_SetValues() described in [http://trac.osgeo.org/postgis/wiki/WKTRaster/SpecificationWorking02 Objective 2.0.05] is still in development. See http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql/st_mapalgebra_optimized.sql The idea is to set large areas of the resulting raster when possible using a process more similar to memcpy than by computing one pixel value at a time.
     230 * A simple PL/pgSQL prototype of the two raster version of ST_MapAlgebra() exists in http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql/st_mapalgebra.sql. This version iterates over every pixel of the unionized extent of two rasters even if there are large areas where both rasters are absent and hence are interpreted as nodata values. An optimized prototype, trying to set those large nodata areas as well as areas where only one raster is present (this is the case when unioning two contiguous non-overlapping rasters) as a block (not pixel by pixel) using ST_SetValues() described in [http://trac.osgeo.org/postgis/wiki/WKTRaster/SpecificationWorking02 Objective 2.0.05] is still in development. See http://trac.osgeo.org/postgis/browser/trunk/raster/scripts/plpgsql/st_mapalgebra_optimized.sql The idea is to set large areas of the resulting raster when possible using a process more similar to memcpy than by computing one pixel value at a time.
    231231
    232232 * Both rasters must have the same SRID. If not, ST_MapAlgebra should return an error: "ERROR:  Operation on two geometries with different SRIDs"