说明

将现有栅格的一个或多个波段返回为新栅格。对于根据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。如果未指定波段或任何指定波段在栅格中不存在，则将返回所有波段。用作各种函数中的帮助函数，例如用于删除波段。

	对于函数的 nbands 文本变体，默认分隔符为 ,，这意味着你可以要求 '1,2,3'，如果你想使用不同的分隔符，则可以执行 ST_Band(rast, '1@2@3', '@')。对于要求多个波段，我们强烈建议你使用此函数的数组形式，例如 ST_Band(rast, '{1,2,3}'::int[]);，因为 text 波段列表形式可能会在 PostGIS 的未来版本中被移除。

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;
                    

另请参阅

ST_AddBand、ST_NumBands、ST_Reclass、第 10 章，栅格参考