Name
ST_ChaikinSmoothing — Returns a smoothed version of a geometry, using the Chaikin algorithm
Synopsis
geometry ST_ChaikinSmoothing(geometry geom, integer nIterations = 1, boolean preserveEndPoints = false);
Descrição
Smoothes a linear or polygonal geometry using Chaikin's algorithm. The degree of smoothing is controlled by the nIterations parameter. On each iteration, each interior vertex is replaced by two vertices located at 1/4 of the length of the line segments before and after the vertex. A reasonable degree of smoothing is provided by 3 iterations; the maximum is limited to 5.
If preserveEndPoints is true, the endpoints of Polygon rings are not smoothed. The endpoints of LineStrings are always preserved.
![[Note]](../images/note.png)
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The number of vertices doubles with each iteration, so the result geometry may have many more points than the input. To reduce the number of points use a simplification function on the result (see ST_Simplify, ST_SimplifyPreserveTopology and ST_SimplifyVW). |
The result has interpolated values for the Z and M dimensions when present.
This function supports 3d and will not drop the z-index.
Availability: 2.5.0
Exemplos
Smoothing a triangle:
SELECT ST_AsText(ST_ChaikinSmoothing(geom)) smoothed
FROM (SELECT 'POLYGON((0 0, 8 8, 0 16, 0 0))'::geometry geom) AS foo;
smoothed
───────────────────────────────────────────
POLYGON((2 2,6 6,6 10,2 14,0 12,0 4,2 2))
Smoothing a Polygon using 1, 2 and 3 iterations:
nIterations = 1 |
nIterations = 2 |
nIterations = 3 |
SELECT ST_ChaikinSmoothing(
'POLYGON ((20 20, 60 90, 10 150, 100 190, 190 160, 130 120, 190 50, 140 70, 120 10, 90 60, 20 20))',
generate_series(1, 3) );
Smoothing a LineString using 1, 2 and 3 iterations:
nIterations = 1 |
nIterations = 2 |
nIterations = 3 |
SELECT ST_ChaikinSmoothing(
'LINESTRING (10 140, 80 130, 100 190, 190 150, 140 20, 120 120, 50 30, 30 100)',
generate_series(1, 3) );