> I think you could easily implement a filter function to remove the 1 pixel > type of > island as a custom function of ST_MapAlgebraFctNgb(). See > http://www.postgis.org/documentation/manual- > svn/RT_ST_MapAlgebraFctNgb.html The size of the window should be 3x3 in this > case. Return the pixel value if at least one neighbour has a value, null > otherwise. > > I am 99% sure ST_MapAlgebraFctNgb would be faster on big rasters than > vectorizing/union/rasterizing... > > However I have no idea how to implement such a filter to remove bigger islands > (or speckles?) spanning on many pixels. Maybe with a little of research...
Actually your first class of pixels to remove have to be 4 pixels. No importance if they are aligned on one row or column? To remove speckles 2x2 you would have a window of 4x4 instead. But this would not remove the OOO O types of arrangement and the O OO O type of arrangement. Pierre _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
