Converting between rasters and geometries
In the last recipe, we used the geometries to filter and clip rasters only to the areas of interest. The ST_Clip() and ST_Intersects() functions implicitly converted the geometry before relating it to the raster.
PostGIS provides several functions for converting rasters to geometries. Depending on the function, a pixel can be returned as an area or a point.
PostGIS provides one function for converting geometries to rasters.
Getting ready
In this recipe, we will convert rasters to geometries, and geometries to rasters. We will use the ST_DumpAsPolygons() and ST_PixelsAsPolygons() functions to convert rasters to geometries. We will then convert geometries to rasters using ST_AsRaster().
How to do it...
Let's adapt part of the query used in the last recipe to find out the average minimum temperature in San Francisco. We replace ST_SummaryStats() with ST_DumpAsPolygons(), and then return the geometries as WKT:
WITH geoms AS (SELECT ST_DumpAsPolygons(ST_Union...
