63 lines
1.7 KiB
PL/PgSQL
63 lines
1.7 KiB
PL/PgSQL
-- {
|
|
-- Return pixel resolution at the given zoom level
|
|
-- }{
|
|
CREATE OR REPLACE FUNCTION @extschema@.CDB_XYZ_Resolution(z INTEGER)
|
|
RETURNS FLOAT8
|
|
AS $$
|
|
-- circumference divided by 256 is z0 resolution, then divide by 2^z
|
|
SELECT 6378137.0*2.0*pi() / 256.0 / power(2.0, z);
|
|
$$ LANGUAGE SQL IMMUTABLE PARALLEL SAFE STRICT;
|
|
-- }
|
|
|
|
-- {
|
|
-- Returns a polygon representing the bounding box of a given XYZ tile
|
|
--
|
|
-- SRID of the returned polygon is forceably 3857
|
|
--
|
|
-- }{
|
|
CREATE OR REPLACE FUNCTION @extschema@.CDB_XYZ_Extent(x INTEGER, y INTEGER, z INTEGER)
|
|
RETURNS GEOMETRY
|
|
AS $$
|
|
DECLARE
|
|
origin_shift FLOAT8;
|
|
initial_resolution FLOAT8;
|
|
tile_geo_size FLOAT8;
|
|
pixres FLOAT8;
|
|
xmin FLOAT8;
|
|
ymin FLOAT8;
|
|
xmax FLOAT8;
|
|
ymax FLOAT8;
|
|
earth_circumference FLOAT8;
|
|
tile_size INTEGER;
|
|
BEGIN
|
|
|
|
-- Size of each tile in pixels (1:1 aspect ratio)
|
|
tile_size := 256;
|
|
|
|
initial_resolution := @extschema@.CDB_XYZ_Resolution(0);
|
|
--RAISE DEBUG 'Initial resolution: %', initial_resolution;
|
|
|
|
origin_shift := (initial_resolution * tile_size) / 2.0;
|
|
-- RAISE DEBUG 'Origin shift (after): %', origin_shift;
|
|
|
|
pixres := initial_resolution / (power(2,z));
|
|
--RAISE DEBUG 'Pixel resolution: %', pixres;
|
|
|
|
tile_geo_size = tile_size * pixres;
|
|
--RAISE DEBUG 'Tile_geo_size: %', tile_geo_size;
|
|
|
|
xmin := -origin_shift + x*tile_geo_size;
|
|
xmax := -origin_shift + (x+1)*tile_geo_size;
|
|
--RAISE DEBUG 'xmin: %', xmin;
|
|
--RAISE DEBUG 'xmax: %', xmax;
|
|
|
|
ymin := origin_shift - y*tile_geo_size;
|
|
ymax := origin_shift - (y+1)*tile_geo_size;
|
|
--RAISE DEBUG 'ymin: %', ymin;
|
|
--RAISE DEBUG 'ymax: %', ymax;
|
|
|
|
RETURN @postgisschema@.ST_MakeEnvelope(xmin, ymin, xmax, ymax, 3857);
|
|
END
|
|
$$ LANGUAGE 'plpgsql' IMMUTABLE STRICT PARALLEL SAFE;
|
|
-- }
|