名称
ST_ValueCount — 返回一组记录，其中包含像素波段值和光栅（或光栅覆盖）中给定波段中具有给定值集的像素数。如果未指定波段，则默认为波段 1。默认情况下，不计算 NoData 值像素。输出像素中的所有其他值和像素波段值都将舍入到最接近的整数。
语法
SETOF record ST_ValueCount(raster rast, integer nband=1, boolean exclude_nodata_value=true, double precision[] searchvalues=NULL, double precision roundto=0, double precision OUT value, integer OUT count);
SETOF record ST_ValueCount(raster rast, integer nband, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count);
SETOF record ST_ValueCount(raster rast, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count);
bigint ST_ValueCount(raster rast, double precision searchvalue, double precision roundto=0);
bigint ST_ValueCount(raster rast, integer nband, boolean exclude_nodata_value, double precision searchvalue, double precision roundto=0);
bigint ST_ValueCount(raster rast, integer nband, double precision searchvalue, double precision roundto=0);
SETOF record ST_ValueCount(text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true, double precision[] searchvalues=NULL, double precision roundto=0, double precision OUT value, integer OUT count);
SETOF record ST_ValueCount(text rastertable, text rastercolumn, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count);
SETOF record ST_ValueCount(text rastertable, text rastercolumn, integer nband, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count);
bigintST_ValueCount(text rastertable, text rastercolumn, integer nband, boolean exclude_nodata_value, double precision searchvalue, double precision roundto=0);
bigint ST_ValueCount(text rastertable, text rastercolumn, double precision searchvalue, double precision roundto=0);
bigint ST_ValueCount(text rastertable, text rastercolumn, integer nband, double precision searchvalue, double precision roundto=0);
描述
返回一组记录，其中包含列 value count，它们包含选定波段的像素波段值和栅格切片或栅格覆盖中的像素计数。
如果未指定波段，则 nband 默认为 1。如果未指定 searchvalues，则将返回栅格或栅格覆盖中找到的所有像素值。如果给定一个 searchvalue，则将返回一个整数（而不是表示具有该像素波段值的像素计数的记录）
![[Note]](../images/note.png) | |
如果将 |
可用性：2.0.0
示例
UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,249) WHERE rid=2;
--Example will count only pixels of band 1 that are not 249. --
SELECT (pvc).*
FROM (SELECT ST_ValueCount(rast) As pvc
FROM dummy_rast WHERE rid=2) As foo
ORDER BY (pvc).value;
value | count
-------+-------
250 | 2
251 | 1
252 | 2
253 | 6
254 | 12
-- Example will coount all pixels of band 1 including 249 --
SELECT (pvc).*
FROM (SELECT ST_ValueCount(rast,1,false) As pvc
FROM dummy_rast WHERE rid=2) As foo
ORDER BY (pvc).value;
value | count
-------+-------
249 | 2
250 | 2
251 | 1
252 | 2
253 | 6
254 | 12
-- Example will count only non-nodata value pixels of band 2
SELECT (pvc).*
FROM (SELECT ST_ValueCount(rast,2) As pvc
FROM dummy_rast WHERE rid=2) As foo
ORDER BY (pvc).value;
value | count
-------+-------
78 | 1
79 | 1
88 | 1
89 | 1
96 | 1
97 | 1
98 | 1
99 | 2
112 | 2
:
--real live example. Count all the pixels in an aerial raster tile band 2 intersecting a geometry
-- and return only the pixel band values that have a count > 500
SELECT (pvc).value, SUM((pvc).count) As total
FROM (SELECT ST_ValueCount(rast,2) As pvc
FROM o_4_boston
WHERE ST_Intersects(rast,
ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
)
) As foo
GROUP BY (pvc).value
HAVING SUM((pvc).count) > 500
ORDER BY (pvc).value;
value | total
-------+-----
51 | 502
54 | 521
-- Just return count of pixels in each raster tile that have value of 100 of tiles that intersect a specific geometry --
SELECT rid, ST_ValueCount(rast,2,100) As count
FROM o_4_boston
WHERE ST_Intersects(rast,
ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
) ;
rid | count
-----+-------
1 | 56
2 | 95
14 | 37
15 | 64