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的栅格。可用于从现有栅格构建新的栅格。

概要

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=,);

描述

返回现有栅格的一个或多个波段作为新的栅格。可用于从现有栅格构建新的栅格，或仅导出栅格的选定波段，或重新排列栅格中波段的顺序。如果没有指定波段，或任何指定的波段在栅格中不存在，则返回所有波段。在各种函数中用作辅助函数，例如删除波段。

[Warning]

对于 nbands 作为文本的函数变体，默认分隔符为 ,，这意味着您可以请求 '1,2,3'，如果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此函数的数组形式，例如 ST_Band(rast, '{1,2,3}'::int[]);，因为 text 类型的波段列表形式可能会在 PostGIS 的未来版本中删除。

可用性：2.0.0

示例

-- Make 2 new rasters: 1 containing band 1 of dummy, second containing band 2 of dummy and then reclassified as a 2BUI
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;

 numb1 | pix1 | numb2 | pix2
-------+------+-------+------
     1 | 8BUI |     1 | 2BUI
                    
-- Return bands 2 and 3. Using array cast syntax
SELECT ST_NumBands(ST_Band(rast, '{2,3}'::int[])) As num_bands
    FROM dummy_rast WHERE rid=2;

num_bands
----------
2

-- Return bands 2 and 3. Use array to define bands
SELECT ST_NumBands(ST_Band(rast, ARRAY[2,3])) As num_bands
    FROM dummy_rast
WHERE rid=2;

原始（列 rast）

dupe_band

sing_band

 
--Make a new raster with 2nd band of original and 1st band repeated twice,
and another with just the third band
SELECT rast, ST_Band(rast, ARRAY[2,1,1]) As dupe_band,
    ST_Band(rast, 3) As sing_band
FROM samples.than_chunked
WHERE rid=35;