Changes between Version 168 and Version 169 of WKTRaster/SpecificationWorking03

Timestamp:

Nov 10, 2011, 1:35:47 PM (12 years ago)

Author:

dzwarg

Comment:

Added open question to ST_MapAlgebraFctNgb

WKTRaster/SpecificationWorking03

@@ -111 +111 @@
  An alternative syntax would involve another function name (e.g. ST_MapAlgebraNgb or ST_MovingWindow) and a way to define a neighbour rectangular region around the computed pixel (e.g.: "2,2" meaning a rectangle encompassing the two neighbour pixels in each direction) and a function to call with this matrix of pixel values. A complete example might look like:
 
-  SELECT ST_MapAlgebraNgb(rast, band, pixeltype, "ST_Mean", 2, 2, "ignore") 
+  SELECT ST_MapAlgebraFctNgb(rast, band, pixeltype, "ST_Mean", 2, 2, "ignore") 
 
  So this would mean "for each pixel, compute the average of all the 1 + 8 + 16 = 25 pixels surrounding the current pixel and "ignore" pixels with nodata values."
@@ -121 +121 @@
   -"value": Replace any nodata value with the value of the pixel being computed.[[BR]]
   -a value: Replace any nodata value with this value and compute.
+
+   '''Open questions'''
+
+   DZ: Since this accepts a user function, the user function should determine how to handle NODATA values inside of the neighborhood. These different modes of operating should be arguments to the userfunctions, and not to ST_MapAlgebraFctNgb.
 
  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).