ST_ValueCount
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名稱

ST_ValueCount — 傳回一組記錄，其中包含網格 (或網格覆蓋範圍) 中指定帶區的像素值，以及具有給定值集合的像素數量。如果未指定帶區，則預設為帶區 1。預設情況下，不會計算 nodata 值像素，並且會輸出像素中的所有其他值，且像素帶區值會四捨五入到最接近的整數。

概要

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

傳回一組具有欄位 value 和 count 的記錄，其中包含所選帶區的網格圖磚或網格覆蓋範圍中的像素帶區值和像素計數。

如果未指定帶區，則 nband 預設為 1。如果未指定 searchvalues，則會傳回在網格或網格覆蓋範圍中找到的所有像素值。如果給定一個 searchvalue，則會傳回一個整數，而不是表示具有該像素帶區值的像素計數的記錄。

[Note]

如果將 exclude_nodata_value 設定為 false，也會計算沒有資料的像素。

可用性：2.0.0

範例

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