ST_Band
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名称

ST_Band — 返回现有栅格的一个或多个波段作为新栅格。 对于从现有栅格构建新栅格非常有用。

大纲

raster ST_Band(raster rast, integer[] nbands = ARRAY[1]);

raster ST_Band(raster rast, integer nband);

raster ST_Band(raster rast, text nbands, character delimiter=,);

Description

返回现有栅格的一个或多个波段作为新栅格。 对于从现有栅格构建新栅格或仅导出栅格的选定波段或重新排列栅格中波段的顺序非常有用。 如果未指定波段或栅格中不存在任何指定波段，则返回所有波段。 用作各种功能中的辅助功能，例如删除波段。

[警告]

对于函数的nbands作为文本变体，默认分隔符是,，这意味着您可以请求'1,2,3'，如果您想使用不同的分隔符，可以使用 ST_Band(rast, '1@2@3', '@')。对于请求多个波段，我们强烈建议您使用这个函数的数组形式，例如 ST_Band(rast, '{1,2,3}'::int[]);，因为 text 格式的波段列表可能会在将来的 PostGIS 版本中被移除。

可用性: 2.0.0

示例

This example creates two rasters: one containing band 1 of dummy_rast, and one containing band 2 reclassified as 2BUI.

Code
SELECT ST_NumBands(rast1) As numb1, ST_BandPixelType(rast1) As pix1,
 ST_NumBands(rast2) As numb2, ST_BandPixelType(rast2) As pix2
FROM (
    SELECT ST_Band(rast) As rast1, ST_Reclass(ST_Band(rast, 3), '100-200):1, [200-254:2', '2BUI') As rast2
        FROM dummy_rast
        WHERE rid = 2) As foo;
栅格输出
numb1 | pix1 | numb2 | pix2
-------+------+-------+------
     1 | 8BUI |     1 | 2BUI

Return bands 2 and 3 using array cast syntax.

Code
SELECT ST_NumBands(ST_Band(rast, '{2,3}'::int[])) As num_bands
FROM dummy_rast WHERE rid=2;
栅格输出
2

Return bands 2 and 3 using array syntax.

Code
SELECT ST_NumBands(ST_Band(rast, ARRAY[2, 3])) As num_bands
    FROM dummy_rast
WHERE rid=2;
栅格输出
2

This example uses three distinct shapes as the red, green, and blue bands of a synthetic raster. It compares the original RGB raster with band 2 followed by band 1 twice, and with band 3 alone.

Code
WITH canvas AS (
    SELECT ST_AddBand(
        ST_AddBand(
            ST_AddBand(
                ST_MakeEmptyRaster(128, 128, 0, 128, 1, -1, 0, 0, 0),
                '8BUI'::text, 0::double precision, 0::double precision
            ),
            '8BUI'::text, 0::double precision, 0::double precision
        ),
        '8BUI'::text, 0::double precision, 0::double precision
    ) AS rast
), bands AS (
    SELECT ST_SetValue(
        ST_SetValue(
            ST_SetValue(rast, 1, ST_Buffer('POINT(32 96)'::geometry, 22), 220),
            2, ST_Buffer('LINESTRING(18 20,110 110)'::geometry, 6,
                         'endcap=flat join=bevel'), 210
        ),
        3, ST_Buffer('LINESTRING(10 48,118 48)'::geometry, 7,
                     'endcap=flat'), 180
    ) AS rast
    FROM canvas
)
SELECT ST_AsPNG(rast) AS "original RGB",
    ST_AsPNG(ST_Band(rast, ARRAY[2, 1, 1])) AS "bands 2,1,1",
    ST_AsPNG(ST_Band(rast, 3)) AS "band 3"
FROM bands;
栅格输出
original RGB                | bands 2,1,1                | band 3
-----------------------------+----------------------------+----------------------------
 PNG image, 128 x 128 pixels | PNG image, 128 x 128 pixels | PNG image, 128 x 128 pixels
Figure
Geometry figure for visual-rt-st-band-04

Band selection from a multi-band raster.

原始（列栅格）

双波段

单波段