Namn
ST_Band — Returnerar ett eller flera band från ett befintligt raster som ett nytt raster. Användbart för att bygga nya raster från befintliga raster.
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=,);
Description
Returnerar ett eller flera band i ett befintligt raster som ett nytt raster. Användbar för att bygga nya raster från befintliga raster eller exportera endast utvalda band i ett raster eller omorganisera ordningen på banden i ett raster. Om inget band anges eller om något av de angivna banden inte finns i rastret returneras alla band. Används som en hjälpfunktion i olika funktioner, t.ex. för att radera ett band.
![[Varning]](../images/warning.png)
|
|
|
För funktionen |
Tillgänglighet: 2.0.0
Exempel
This example creates two rasters: one containing band 1 of dummy_rast, and one containing band 2 reclassified as 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;
2
Return bands 2 and 3 using array syntax.
SELECT ST_NumBands(ST_Band(rast, ARRAY[2, 3])) As num_bands
FROM dummy_rast
WHERE rid=2;
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.
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;
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
Band selection from a multi-band raster.
original (kolumn rast) |
dupe_band |
sing_band |