- box(circle)
描述：将圆转换成矩形
返回类型：box
示例：
gbase=# SELECT box(circle '((0,0),2.0)') AS RESULT;
result
---------------------------------------------------------------------------
(1.41421356237309,1.41421356237309),(-1.41421356237309,-1.41421356237309)
(1 row)
- box(point, point)
描述：将点转换成矩形
返回类型：box
示例：
gbase=# SELECT box(point '(0,0)', point '(1,1)') AS RESULT;
result
-------------
(1,1),(0,0)
(1 row)
- box(polygon)
描述：将多边形转换成矩形
返回类型：box
示例：
gbase=# SELECT box(polygon '((0,0),(1,1),(2,0))') AS RESULT;
result
-------------
(2,1),(0,0)
(1 row)
- circle(box)
描述：矩形转换成圆
返回类型：circle
示例：
gbase=# SELECT circle(box '((0,0),(1,1))') AS RESULT;
result
-------------------------------
<(0.5,0.5),0.707106781186548>
(1 row)
- circle(point, double precision)
描述：将圆心和半径转换成圆
返回类型：circle
示例：
gbase=# SELECT circle(point '(0,0)', 2.0) AS RESULT;
result
-----------
<(0,0),2>
(1 row)
- circle(polygon)
描述：将多边形转换成圆
返回类型：circle
示例：
gbase=# SELECT circle(polygon '((0,0),(1,1),(2,0))') AS RESULT;
result
-------------------------------------------
<(1,0.333333333333333),0.924950591148529>
(1 row)
- lseg(box)
描述：矩形对角线转化成线段
返回类型：lseg
示例：
gbase=# SELECT lseg(box '((-1,0),(1,0))') AS RESULT;
result
----------------
[(1,0),(-1,0)]
(1 row)
- lseg(point, point)
描述：点转换成线段
返回类型：lseg
示例：
gbase=# SELECT lseg(point '(-1,0)', point '(1,0)') AS RESULT;
result
----------------
[(-1,0),(1,0)]
(1 row)
- slope(point, point)
描述：计算两个点构成直线的斜率
返回类型: double
示例：
gbase=# SELECT slope(point '(1,1)', point '(0,0)') AS RESULT;
result
--------
1
(1 row)
- path(polygon)
描述：多边形转换成路径
返回类型：path
示例：
gbase=# SELECT path(polygon '((0,0),(1,1),(2,0))') AS RESULT;
result
---------------------
((0,0),(1,1),(2,0))
(1 row)
- point(double precision, double precision)
描述：节点
返回类型：point
示例：
gbase=# SELECT point(23.4, -44.5) AS RESULT;
result
--------------
(23.4,-44.5)
(1 row)
- point(box)
描述：矩形的中心
返回类型：point
示例：
gbase=# SELECT point(box '((-1,0),(1,0))') AS RESULT;
result
--------
(0,0)
(1 row)
- point(circle)
描述：圆心
返回类型：point
示例：
gbase=# SELECT point(circle '((0,0),2.0)') AS RESULT;
result
--------
(0,0)
(1 row)
- point(lseg)
描述：线段的中心
返回类型：point
示例：
gbase=# SELECT point(lseg '((-1,0),(1,0))') AS RESULT;
result
--------
(0,0)
(1 row)
- point(polygon)
描述：多边形的中心
返回类型：point
示例：
gbase=# SELECT point(polygon '((0,0),(1,1),(2,0))') AS RESULT;
result
-----------------------
(1,0.333333333333333)
(1 row)
- polygon(box)
描述：矩形转换成4点多边形
返回类型：polygon
示例：
gbase=# SELECT polygon(box '((0,0),(1,1))') AS RESULT;
result
---------------------------
((0,0),(0,1),(1,1),(1,0))
(1 row)
- polygon(circle)
描述：圆转换成12点多边形
返回类型：polygon
示例：
gbase=# SELECT polygon(circle '((0,0),2.0)') AS RESULT;
result
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
((-2,0),(-1.73205080756888,1),(-1,1.73205080756888),(-1.22464679914735e-16,2),(1,1.73205080756888),(1.73205080756888,1),(2,2.44929359829471e-16),(1.73205080756888,-0.999999999999999),(1,-1.73205080756888),(3.67394039744206e-16,-2),(-0.999999999999999,-1.73205080756888),(-1.73205080756888,-1))
(1 row)
- polygon(npts, circle)
描述：圆转换成npts点多边形
返回类型：polygon
示例：
gbase=# SELECT polygon(12, circle '((0,0),2.0)') AS RESULT;
result
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
((-2,0),(-1.73205080756888,1),(-1,1.73205080756888),(-1.22464679914735e-16,2),(1,1.73205080756888),(1.73205080756888,1),(2,2.44929359829471e-16),(1.73205080756888,-0.999999999999999),(1,-1.73205080756888),(3.67394039744206e-16,-2),(-0.999999999999999,-1.73205080756888),(-1.73205080756888,-1))
(1 row)
- polygon(path)
描述：路径转换成多边形
返回类型：polygon
示例：
gbase=# SELECT polygon(path '((0,0),(1,1),(2,0))') AS RESULT;
result
---------------------
((0,0),(1,1),(2,0))
(1 row)
