ST_Band
Prev  11.3. 栅格构造器  Next

Name

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。

Synopsis

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。

[Warning]

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

-- 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（列栅格）

双波段

单波段

 
--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;