描述

将普通的 LINESTRING/POLYGON 转换为 CIRCULAR STRING 和曲线多边形。请注意，描述曲线等效项所需的点要少得多。

	如果输入的 LINESTRING/POLYGON 曲率不足以清晰地表示曲线，则该函数将返回相同的输入几何。

可用性：1.3.0

此函数支持 3d，并且不会丢弃 z 索引。

此方法支持圆形字符串和曲线。

示例

 -- 2D Example
SELECT ST_AsText(ST_LineToCurve(foo.geom)) As curvedastext,ST_AsText(foo.geom) As non_curvedastext
    FROM (SELECT ST_Buffer('POINT(1 3)'::geometry, 3) As geom) As foo;

curvedatext                                                            non_curvedastext
--------------------------------------------------------------------|-----------------------------------------------------------------
CURVEPOLYGON(CIRCULARSTRING(4 3,3.12132034355964 0.878679656440359, | POLYGON((4 3,3.94235584120969 2.41472903395162,3.77163859753386 1.85194970290473,
1 0,-1.12132034355965 5.12132034355963,4 3))                        |  3.49440883690764 1.33328930094119,3.12132034355964 0.878679656440359,
                                                                    |  2.66671069905881 0.505591163092366,2.14805029709527 0.228361402466141,
                                                                    |  1.58527096604839 0.0576441587903094,1 0,
                                                                    |  0.414729033951621 0.0576441587903077,-0.148050297095264 0.228361402466137,
                                                                    |  -0.666710699058802 0.505591163092361,-1.12132034355964 0.878679656440353,
                                                                    |  -1.49440883690763 1.33328930094119,-1.77163859753386 1.85194970290472
                                                                    |  --ETC-- ,3.94235584120969 3.58527096604839,4 3))

--3D example
SELECT ST_AsText(ST_LineToCurve(geom)) As curved, ST_AsText(geom) AS not_curved
FROM (SELECT ST_Translate(ST_Force3D(ST_Boundary(ST_Buffer(ST_Point(1,3), 2,2))),0,0,3) AS geom) AS foo;

                        curved                        |               not_curved
------------------------------------------------------+---------------------------------------------------------------------
 CIRCULARSTRING Z (3 3 3,-1 2.99999999999999 3,3 3 3) | LINESTRING Z (3 3 3,2.4142135623731 1.58578643762691 3,1 1 3,
                                                      | -0.414213562373092 1.5857864376269 3,-1 2.99999999999999 3,
                                                      | -0.414213562373101 4.41421356237309 3,
                                                      | 0.999999999999991 5 3,2.41421356237309 4.4142135623731 3,3 3 3)
(1 row)

另请参见

ST_CurveToLine