ST_ValueCount
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Name

ST_ValueCount — Retorna o conjunto de registros contendo uma banda pixel de valor e conta do número de pixeis em uma dada banda de um raster (ou uma cobertura raster) que tem um dado conjunto de valores. Usa-se a banda 1 se nenhuma for especificada. Por padrão pixeis de valor nodata não são contados. Todos os outros valores no pixel são saída e os valores de pixeis são arredondados para o inteiro mais próximo.

Synopsis

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);

Descrição

Retorna um conjunto de registros com colunas value count que contêm o valor da banda pixel e soma de pixeis na tile raster ou cobertura raster da banda selecionada.

Se nenhuma banda for especificada nband usa-se 1. Se nenhum searchvalues for especificado, retornarão pixeis com valores encontrados no raster ou cobertura raster. Se um valor de pesquisa for dado, retornará um inteiro em vez de registros indicando a soma de pixeis que têm aquele valor de banda pixel

[Note]

Se exclude_nodata_value for falso, contará também pixeis sem dados.

Disponibilidade: 2.0.0

Exemplos

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