PolarDB:ST_HMTAsRaster

Syntax

raster ST_HMTAsArray(bytea hmt, text storageOption default '{}');

Parameters

Usage notes

• The spatial reference (SRID) of the input geometry must match the spatial reference used when generating the heatmap with ST_AsHMT.

• When storageOption is omitted or set to '{}', the raster is stored in an anonymous temporary table.

Description

ST_HMTAsRaster converts heatmap tiles into raster objects. Heatmap tiles are generated by ST_AsHMT, making these two functions complementary steps in the same workflow: ST_AsHMT produces a protobuf-encoded heatmap tile from geometry data, and ST_HMTAsRaster converts that tile back into a raster for rendering or further computation.

Examples

The following example creates a test table with point geometry, weight, and volume columns, generates a heatmap tile with ST_AsHMT, and converts it to a raster with ST_HMTAsRaster. The storageOption parameter is omitted, so the raster is stored in an anonymous temporary table.

CREATE TABLE test_table AS
SELECT i num,
    ST_setSRID(st_makepoint((i-0.5)::numeric, (i-0.5)::numeric), 4326) geom,
    i*100::int4 weight,
    i*i*i::float8 volume
FROM generate_series(1, 10) i;

SELECT ST_HMTAsRaster(ST_AsHMT(geom, --geometry type
    ST_MakeEnvelope(0, 0, 10, 10, 4326), -- Extent
    10,        -- Width, in pixel
    10        -- height
))
FROM test_table;
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See also

• ST_AsHMT — generates a protobuf-encoded heatmap tile from geometry data

• ST_CreateRast — reference for storageOption parameters