ST_ReclassExact
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Name

ST_ReclassExact — 创建一个新栅格，其波段通过对原始波段进行 1:1 映射重分类生成，将原波段中的值映射为目标波段中的新值。

Synopsis

raster ST_ReclassExact(raster rast, double precision[] inputvalues, double precision[] outputvalues, integer bandnumber=1, text pixeltype=32BF, double precision nodatavalue=NULL);

描述

根据 inputvalues 和 outputvalues 数组定义的重分类操作，生成一个新的栅格。输入栅格中与数组匹配的像元值将被映射为对应的值，所有未匹配的像元值将被映射为 nodatavalue。

输出像元类型默认设为 float，但可通过 pixeltype 参数进行指定。若未指定 bandnumber，则默认使用第 1 波段。

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

可用性：3.6.0

示例：基础用法

创建一个小型栅格，并将其像元映射为新的值。

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;