Add raster zxy function doc and test

Author: sharkAndshark

tests/fixtures/functions/function_zxy_raster.sql

@@ -0,0 +1,19 @@
+DROP FUNCTION IF EXISTS public.function_zxy_raster;
+
+CREATE OR REPLACE FUNCTION public.function_zxy_raster(z integer, x integer, y integer) RETURNS bytea AS $$
+DECLARE
+  mvt bytea;
+BEGIN
+  with rast as (
+    SELECT
+    st_clip(
+        st_transform(st_union(rast),3857),
+        st_tileenvelope(z,x,y) 
+    )
+    as bands
+    from public.landcover where ST_ConvexHull(rast) && st_transform( st_tileenvelope(z,x,y),4326) 
+  )
+  SELECT into mvt ST_AsJPEG(st_tile(bands,256,256)) from rast;
+  return mvt;
+END
+$$ LANGUAGE plpgsql IMMUTABLE STRICT PARALLEL SAFE;

tests/fixtures/initdb.sh

@@ -26,6 +26,11 @@ for sql_file in "$FIXTURES_DIR"/tables/*.sql; do
   psql -e -P pager=off -v ON_ERROR_STOP=1 -f "$sql_file"
 done
 
+echo "Importing raster tables from $FIXTURES_DIR/raster"
+echo "################################################################################################"
+psql -e -P pager=off -v ON_ERROR_STOP=1 -f "$FIXTURES_DIR"/raster/init_raster_support.sql
+raster2pgsql -s 4326 -I  -C -F -t 100x100 "$FIXTURES_DIR"/raster/raster.tif public.landcover | psql -e -P pager=off -v ON_ERROR_STOP=1 
+
 echo -e "\n\n\n"
 echo "################################################################################################"
 echo "Importing functions from $FIXTURES_DIR/functions"

tests/fixtures/raster/init_raster_support.sql

@@ -0,0 +1,4 @@
+create extension postgis_raster;
+alter DATABASE db SET postgis.enable_outdb_rasters = true;
+alter DATABASE db set postgis.gdal_enabled_drivers To  'GTiff PNG JPEG';
+SELECT pg_reload_conf();