Changes between Version 110 and Version 111 of WKTRaster/SpecificationWorking03


Ignore:
Timestamp:
06/13/11 15:08:11 (14 years ago)
Author:
pracine
Comment:

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  • WKTRaster/SpecificationWorking03

    v110 v111  
    113113 The "ST_Mean" summarizing function should accept three parameters: an array of float8 values, a X and a Y dimension, and optionnally a "what to do with nodata values". The possible value for this last parameter could be:
    114114
    115  * "NULL": If any value is a nodata value, return NULL.
    116  * "ignore": Ignore any nodata value so that if 4 pixels on 25 are nodata values, do the computation with the 21 remaining. This is the default.
    117  * "value": Replace any nodata value with the value of the pixel being computed.
    118  * a value: Replace any nodata value with this value and compute.
     115  -"NULL": If any value is a nodata value, return NULL.[[BR]]
     116  -"ignore": Ignore any nodata value so that if 4 pixels on 25 are nodata values, do the computation with the 21 remaining. This is the default.[[BR]]
     117  -"value": Replace any nodata value with the value of the pixel being computed.[[BR]]
     118  -a value: Replace any nodata value with this value and compute.
    119119
    120120 Any remaining parameters to ST_MapAlgebraNgb could be passed to the summarizing functions for its own need (e.g. "round" to specify that only the pixel forming a circle should be used in the computing).
    … …  
    136136 Three difficulties must be solved to implement this function:
    137137
    138  * The construction of the matrix must to be passed to the summarizing functions must be optimized when passing from one pixel to the other.
    139  * We must see how it is possible to call a PL/pgSQL function from a C function
    140  * We must see how to pass a variable number of parameter to a PL/pgSQL function
     138  -The construction of the matrix must to be passed to the summarizing functions must be optimized when passing from one pixel to the other.[[BR]]
     139  -We must see how it is possible to call a PL/pgSQL function from a C function[[BR]]
     140  -We must see how to pass a variable number of parameter to a PL/pgSQL function
    141141
    142142 See also: [wiki:WKTRaster/MapAlgebra Notes taken by David Zwarg during the Montreal Code Sprint 2011] and http://trac.osgeo.org/postgis/ticket/860
    … …  
    161161 Replacement expressions can be provided as parameter for when:
    162162
    163   -The first raster value is nodata
    164   -The second raster value is nodata
     163  -The first raster value is nodata[[BR]]
     164  -The second raster value is nodata[[BR]]
    165165  -Both rasters values when they are both nodata
    166166