8000 Fix OffsetCurve to use a minimum QuadrantSegs value by dr-jts · Pull Request #981 · locationtech/jts · GitHub
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Fix OffsetCurve to use a minimum QuadrantSegs value #981

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Merged
merged 2 commits into from
May 26, 2023
Merged

Fix OffsetCurve to use a minimum QuadrantSegs value #981

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41eb491
Enforce a minimum QuadrantSegs value
dr-jts May 25, 2023
0d1befb
Add unit tests
dr-jts May 26, 2023
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16 changes: 15 additions & 1 deletion modules/core/src/main/java/org/locationtech/jts/operation/buffer/OffsetCurve.java
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,12 @@ public class OffsetCurve {
* The nearness tolerance for matching the the raw offset linework and the buffer curve.
*/
private static final int MATCH_DISTANCE_FACTOR = 10000;

/**
* A QuadSegs minimum value that will prevent generating
* unwanted offset curve artifacts near end caps.
*/
private static final int MIN_QUADRANT_SEGMENTS = 8;

/**
* Computes the offset curve of a geometry at a given distance.
Expand Down Expand Up @@ -164,7 +170,15 @@ public OffsetCurve(Geometry geom, double distance, BufferParameters bufParams) {
//-- make new buffer params since the end cap style must be the default
this.bufferParams = new BufferParameters();
if (bufParams != null) {
bufferParams.setQuadrantSegments(bufParams.getQuadrantSegments());
/**
* Prevent using a very small QuadSegs value, to avoid
* offset curve artifacts near the end caps.
*/
int quadSegs = bufParams.getQuadrantSegments();
if (quadSegs < MIN_QUADRANT_SEGMENTS) {
quadSegs = MIN_QUADRANT_SEGMENTS;
}
bufferParams.setQuadrantSegments(quadSegs);
bufferParams.setJoinStyle(bufParams.getJoinStyle());
bufferParams.setMitreLimit(bufParams.getMitreLimit());
}
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22 changes: 20 additions & 2 deletions modules/core/src/test/java/org/locationtech/jts/operation/buffer/OffsetCurveTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -298,8 +298,8 @@ public void testInfiniteLoop() {
public void testQuadSegs() {
checkOffsetCurve(
"LINESTRING (20 20, 50 50, 80 20)",
10, 2, -1, -1,
"LINESTRING (12.93 27.07, 42.93 57.07, 50 60, 57.07 57.07, 87.07 27.07)"
10, 10, -1, -1,
"LINESTRING (12.93 27.07, 42.93 57.07, 44.12 58.09, 45.46 58.91, 46.91 59.51, 48.44 59.88, 50 60, 51.56 59.88, 53.09 59.51, 54.54 58.91, 55.88 58.09, 57.07 57.07, 87.07 27.07)"
);
}

Expand All @@ -319,6 +319,24 @@ public void testJoinMitre() {
);
}

// See https://github.com/qgis/QGIS/issues/53165
public void testMinQuadrantSegments() {
checkOffsetCurve(
"LINESTRING (553772.0645892698 177770.05079236583, 553780.9235869241 177768.99614978794, 553781.8325485934 177768.41771963477)",
-11, 0, BufferParameters.JOIN_MITRE, -1,
"LINESTRING (553770.76 177759.13, 553777.54 177758.32)"
);
}

// See https://github.com/qgis/QGIS/issues/53165#issuecomment-1563214857
public void testMinQuadrantSegments_QGIS() {
checkOffsetCurve(
"LINESTRING (421 622, 446 625, 449 627)",
133, 0, BufferParameters.JOIN_MITRE, -1,
"LINESTRING (405.15 754.05, 416.3 755.39)"
);
}

//=======================================

private static final double EQUALS_TOL = 0.05;
Expand Down
0