ST_Scale
Prev  7.16. Affine Transformations  Next

Name

ST_Scale — Scales a geometry by given factors.

Synopsis

geometry ST_Scale(geometry geomA, float XFactor, float YFactor, float ZFactor);

geometry ST_Scale(geometry geomA, float XFactor, float YFactor);

geometry ST_Scale(geometry geom, geometry factor);

geometry ST_Scale(geometry geom, geometry factor, geometry origin);

Description

Scales the geometry to a new size by multiplying the ordinates with the corresponding factor parameters.

The version taking a geometry as the factor parameter allows passing a 2d, 3dm, 3dz or 4d point to set scaling factor for all supported dimensions. Missing dimensions in the factor point are equivalent to no scaling the corresponding dimension.

The three-geometry variant allows a "false origin" for the scaling to be passed in. This allows "scaling in place", for example using the centroid of the geometry as the false origin. Without a false origin, scaling takes place relative to the actual origin, so all coordinates are just multiplied by the scale factor.

[Note]

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.2.0 support for scaling all dimension (factor parameter) was introduced.

Enhanced: 2.5.0 support for scaling relative to a local origin (origin parameter) was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports M coordinates.

Examples

This example scales X, Y, and Z values.

Code
SELECT ST_Scale('LINESTRING(1 2 3,1 1 1)', 0.5, 0.75, 0.8);
Output
LINESTRING(0.5 1.5 2.4,0.5 0.75 0.8)
Figure
Geometry figure for visual-st-scale-01

This example scales X and Y values.

Code
SELECT ST_Scale('LINESTRING(1 2 3,1 1 1)', 0.5, 0.75);
Output
LINESTRING(0.5 1.5 3,0.5 0.75 1)
Figure
Geometry figure for visual-st-scale-02

This example scales X, Y, Z, and M values.

Code
SELECT ST_Scale('LINESTRING(1 2 3 4,1 1 1 1)',
    ST_MakePoint(0.5, 0.75, 2, -1));
Output
LINESTRING(0.5 1.5 6 -4,0.5 0.75 2 -1)
Figure
Geometry figure for visual-st-scale-03

This example scales X and Y values using a false origin.

Code
SELECT ST_Scale('LINESTRING(1 1,2 2)', 'POINT(2 2)', 'POINT(1 1)'::geometry);
Output
LINESTRING(1 1,3 3)
Figure
Geometry figure for visual-st-scale-04

This example constructs an ellipse centered at (10, 20), with X radius 8, Y radius 4, and rotated 30 degrees counter-clockwise. Scaling and rotation use the center as their origin, so the ellipse keeps both its position and SRID.

Code
WITH params AS (
  SELECT
    ST_SetSRID(ST_Point(10, 20), 3857) AS center,
    8.0 AS x_radius,
    4.0 AS y_radius,
    radians(30) AS angle
)
SELECT ST_Rotate(
         ST_Scale(
           ST_Buffer(center, 1, 'quad_segs=32'),
           ST_MakePoint(x_radius, y_radius),
           center
         ),
         angle,
         center
       ) AS ellipse
FROM params;