ST_Reclass
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## Name

ST_Reclass — Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.

## Synopsis

`raster ST_Reclass(`raster rast, integer nband, text reclassexpr, text pixeltype, double precision nodataval=NULL`)`;

`raster ST_Reclass(`raster rast, reclassarg[] VARIADIC reclassargset`)`;

`raster ST_Reclass(`raster rast, text reclassexpr, text pixeltype`)`;

## Description

Creates a new raster formed by applying a valid PostgreSQL algebraic operation defined by the `reclassexpr` on the input raster (`rast`). If no `band` is specified band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster. Bands not designated will come back unchanged. Refer to reclassarg for description of valid reclassification expressions.

The bands of the new raster will have pixel type of `pixeltype`. If `reclassargset` is passed in then each reclassarg defines behavior of each band generated.

Availability: 2.0.0

## Examples Basic

Create a new raster from the original where band 2 is converted from 8BUI to 4BUI and all values from 101-254 are set to nodata value.

    ALTER TABLE dummy_rast ADD COLUMN reclass_rast raster;
    UPDATE dummy_rast SET reclass_rast = ST_Reclass(rast,2,'0-87:1-10, 88-100:11-15, 101-254:0-0', '4BUI',0) WHERE rid = 2;

    SELECT i as col, j as row, ST_Value(rast,2,i,j) As origval,
        ST_Value(reclass_rast, 2, i, j) As reclassval,
        ST_Value(reclass_rast, 2, i, j, false) As reclassval_include_nodata
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     col | row | origval | reclassval | reclassval_include_nodata
    -----+-----+---------+------------+---------------------------
       1 |   1 |      78 |          9 |                         9
       2 |   1 |      98 |         14 |                        14
       3 |   1 |     122 |            |                         0
       1 |   2 |      96 |         14 |                        14
       2 |   2 |     118 |            |                         0
       3 |   2 |     180 |            |                         0
       1 |   3 |      99 |         15 |                        15
       2 |   3 |     112 |            |                         0
       3 |   3 |     169 |            |                         0

## Example: Advanced using multiple reclassargs

Create a new raster from the original where band 1,2,3 is converted to 1BB,4BUI, 4BUI respectively and reclassified. Note this uses the variadic `reclassarg` argument which can take as input an indefinite number of reclassargs (theoretically as many bands as you have)

    UPDATE dummy_rast SET reclass_rast =
        ST_Reclass(rast,
            ROW(2,'0-87]:1-10, (87-100]:11-15, (101-254]:0-0', '4BUI',NULL)::reclassarg,
            ROW(1,'0-253]:1, 254:0', '1BB', NULL)::reclassarg,
            ROW(3,'0-70]:1, (70-86:2, [86-150):3, [150-255:4', '4BUI', NULL)::reclassarg
            ) WHERE rid = 2;

    SELECT i as col, j as row,ST_Value(rast,1,i,j) As ov1,  ST_Value(reclass_rast, 1, i, j) As rv1,
        ST_Value(rast,2,i,j) As ov2, ST_Value(reclass_rast, 2, i, j) As rv2,
        ST_Value(rast,3,i,j) As ov3, ST_Value(reclass_rast, 3, i, j) As rv3
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

    col | row | ov1 | rv1 | ov2 | rv2 | ov3 | rv3
    ----+-----+-----+-----+-----+-----+-----+-----
      1 |   1 | 253 |   1 |  78 |   9 |  70 |   1
      2 |   1 | 254 |   0 |  98 |  14 |  86 |   3
      3 |   1 | 253 |   1 | 122 |   0 | 100 |   3
      1 |   2 | 253 |   1 |  96 |  14 |  80 |   2
      2 |   2 | 254 |   0 | 118 |   0 | 108 |   3
      3 |   2 | 254 |   0 | 180 |   0 | 162 |   4
      1 |   3 | 250 |   1 |  99 |  15 |  90 |   3
      2 |   3 | 254 |   0 | 112 |   0 | 108 |   3
      3 |   3 | 254 |   0 | 169 |   0 | 175 |   4

## Example: Advanced Map a single band 32BF raster to multiple viewable bands

Create a new 3 band (8BUI,8BUI,8BUI viewable raster) from a raster that has only one 32bf band

    ALTER TABLE wind ADD COLUMN rast_view raster;
    UPDATE wind
        set rast_view = ST_AddBand( NULL,
            ARRAY[
        ST_Reclass(rast, 1,'0.1-10]:1-10,9-10]:11,(11-33:0'::text, '8BUI'::text,0),
        ST_Reclass(rast,1, '11-33):0-255,[0-32:0,(34-1000:0'::text, '8BUI'::text,0),
        ST_Reclass(rast,1,'0-32]:0,(32-100:100-255'::text, '8BUI'::text,0)
        ]
        );

## See Also

ST_AddBand, ST_Band, ST_BandPixelType, ST_MakeEmptyRaster, reclassarg, ST_Value

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