ST_ReclassExact

Description

Creates a new raster formed by applying a reclassification operation defined by the inputvalues and outputvalues arrays. Pixel values found in the input array are mapped to the corresponding value in the output array. All other pixel values are mapped to the nodatavalue .

The output pixel type defaults to float, but can be specified using the pixeltype parameter. If no bandnumber is specified band 1 is assumed.

The new raster will have the same georeference, width, and height as the original raster. Bands not designated are returned unchanged.

Availability: 3.6.0

Example: Basic

Create a small raster and map its pixels to new values.

CREATE TABLE reclassexact (
	id integer,
	rast raster
);

--
-- Create a raster with just four pixels
-- [1  2]
-- [3  4]
--
INSERT INTO reclassexact (id, rast)
SELECT 1, ST_SetValues(
    ST_AddBand(
      ST_MakeEmptyRaster(
        2,    -- width in pixels
        2,    -- height in pixels
        0,    -- upper-left x-coordinate
        0,    -- upper-left y-coordinate
        1,    -- pixel size in x-direction
        -1,   -- pixel size in y-direction (negative for north-up)
        0,    -- skew in x-direction
        0,    -- skew in y-direction
        4326  -- SRID (e.g., WGS 84)
      ),
      '32BUI'::text, -- pixel type (e.g., '32BF' for float, '8BUI' for unsigned 8-bit int)
      0.0,           -- initial value for the band (e.g., 0.0 or a no-data value)
      -99            -- nodatavalue
    ),
    1, -- band number (usually 1 for single-band rasters)
    1, -- x origin for setting values (usually 1)
    1, -- y origin for setting values (usually 1)
    ARRAY[
      ARRAY[1, 2],
      ARRAY[3, 4]
    ]::double precision[][] -- 2D array of values
  );

-- Reclass the values to new values
-- and dump the values of the new raster for display
WITH rc AS (
  SELECT ST_ReclassExact(
    rast,                -- input raster
    ARRAY[4,3,2,1],      -- input map
    ARRAY[14,13,12,11],  -- output map
    1,                   -- band number to remap
    '32BUI'              -- output raster pixtype
    ) AS rast
  FROM reclassexact
  WHERE id = 1
  )
SELECT 'rce-1', (ST_DumpValues(rc.rast)).*
FROM rc;
                    

See Also

ST_Reclass , ST_AddBand , ST_Band , ST_MakeEmptyRaster