ST_Polygonize
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名稱

ST_Polygonize — 計算由一組幾何圖形的線條所形成的複數多邊形。

概要

geometry ST_Polygonize(geometry set geomfield);

geometry ST_Polygonize(geometry[] geom_array);

描述

建立一個 GeometryCollection，其中包含由一組幾何圖形的線條所形成的多邊形。如果輸入的線條沒有形成任何多邊形，則會返回一個空的 GeometryCollection。

此函數會建立涵蓋所有劃定區域的多邊形。如果結果旨在形成有效的多邊形幾何圖形，請使用 ST_BuildArea 以防止孔洞被填滿。

[Note]

輸入的線條必須正確節點化，此函數才能正常運作。為了確保輸入已節點化，請在多邊形化之前對輸入幾何圖形使用 ST_Node。
[Note]

GeometryCollection 可能難以使用外部工具處理。使用 ST_Dump 將多邊形化結果轉換為獨立的多邊形。

由 GEOS 模組執行。

可用性：1.0.0RC1

範例

輸入線條

多邊形化結果

 
WITH data(geom) AS (VALUES
   ('LINESTRING (180 40, 30 20, 20 90)'::geometry)
  ,('LINESTRING (180 40, 160 160)'::geometry)
  ,('LINESTRING (80 60, 120 130, 150 80)'::geometry)
  ,('LINESTRING (80 60, 150 80)'::geometry)
  ,('LINESTRING (20 90, 70 70, 80 130)'::geometry)
  ,('LINESTRING (80 130, 160 160)'::geometry)
  ,('LINESTRING (20 90, 20 160, 70 190)'::geometry)
  ,('LINESTRING (70 190, 80 130)'::geometry)
  ,('LINESTRING (70 190, 160 160)'::geometry)
)
SELECT ST_AsText( ST_Polygonize( geom ))
    FROM data;

------------------------------------------------------------------------------------------
GEOMETRYCOLLECTION (POLYGON ((180 40, 30 20, 20 90, 70 70, 80 130, 160 160, 180 40), (150 80, 120 130, 80 60, 150 80)),
                    POLYGON ((20 90, 20 160, 70 190, 80 130, 70 70, 20 90)),
                    POLYGON ((160 160, 80 130, 70 190, 160 160)),
                    POLYGON ((80 60, 120 130, 150 80, 80 60)))

多邊形化線字串表格

SELECT ST_AsEWKT(ST_Polygonize(geom_4269)) As geomtextrep
FROM (SELECT geom_4269 FROM ma.suffolk_edges) As foo;

-------------------------------------
 SRID=4269;GEOMETRYCOLLECTION(POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,-71.040878 42.285678)),
 POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358,-71.171794 42.354971,-71.170511 42.354855,
 -71.17112 42.354238,-71.17166 42.353675)))

--Use ST_Dump to dump out the polygonize geoms into individual polygons
SELECT ST_AsEWKT((ST_Dump(t.polycoll)).geom) AS geomtextrep
FROM (SELECT ST_Polygonize(geom_4269) AS polycoll
    FROM (SELECT geom_4269 FROM ma.suffolk_edges)
        As foo) AS t;

------------------------
 SRID=4269;POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,
-71.040878 42.285678))
 SRID=4269;POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358
,-71.171794 42.354971,-71.170511 42.354855,-71.17112 42.354238,-71.17166 42.353675))

另請參閱

ST_BuildArea、ST_Dump、ST_Node