[postgis-users] Extracting cell values into a matrix

[DavidRA]

The number of input rasters is unknown, the user decides how many will get
involved. The weights are given also by the user. Let's say that he wants to
compute the OWA over four rasters with the weights 0.1, 0.2, 0.3 and 0.4.

Then, the external tool should connect to a PostGIS database, extract the
matrices of each raster and begin the calculation: for each position,
extract the value of every matrix and assign those values with a weight
accordingly to the order. If the four pixels extracted from position (1,1)
are 4, 7, 1 and 3, the assignation would be:

- Value 1 -> weight 0.1
- Value 3 -> weight 0.2
- Value 4 -> weight 0.3
- Value 7 -> weight 0.4

With this, the OWA can be computed and the result would be stored on
position (1,1) of the output raster.

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