* Port locationtech/jts#981

* References qgis/QGIS#53165 * References #897
libgeos · May 29, 2023 · 68a5b4d · 68a5b4d
1 parent 523cea8
commit 68a5b4d
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Showing 4 changed files with 48 additions and 5 deletions.
diff --git a/include/geos/operation/buffer/OffsetCurve.h b/include/geos/operation/buffer/OffsetCurve.h
@@ -190,6 +190,12 @@ class GEOS_DLL OffsetCurve {
     // Constants
     static constexpr int MATCH_DISTANCE_FACTOR = 10000;
 
+    /**
+    * A QuadSegs minimum value that will prevent generating
+    * unwanted offset curve artifacts near end caps.
+    */
+    static constexpr int MIN_QUADRANT_SEGMENTS = 8;
+
     /**
     * Creates a new instance for computing an offset curve for a geometry at a given distance.
     * with default quadrant segments (BufferParameters::DEFAULT_QUADRANT_SEGMENTS)
@@ -230,7 +236,17 @@ class GEOS_DLL OffsetCurve {
                 throw util::IllegalArgumentException("OffsetCurve distance must be a finite value");
             }
             //-- set buffer params, leaving cap style as the default CAP_ROUND
-            bufferParams.setQuadrantSegments( bp.getQuadrantSegments());
+
+            /**
+            * Prevent using a very small QuadSegs value, to avoid
+            * offset curve artifacts near the end caps.
+            */
+            int quadSegs = bp.getQuadrantSegments();
+            if (quadSegs < MIN_QUADRANT_SEGMENTS) {
+                quadSegs = MIN_QUADRANT_SEGMENTS;
+            }
+            bufferParams.setQuadrantSegments(quadSegs);
+
             bufferParams.setJoinStyle( bp.getJoinStyle());
             bufferParams.setMitreLimit( bp.getMitreLimit());
         };

diff --git a/tests/unit/capi/GEOSOffsetCurveTest.cpp b/tests/unit/capi/GEOSOffsetCurveTest.cpp
@@ -104,7 +104,7 @@ void object::test<3>()
 {
      checkOffset(
         "LINESTRING(0 0, 10 0, 10 10)",
-        "LINESTRING (12 10, 12 0, 10 -2, 0 -2)",
+        "LINESTRING (0 -2, 10 -2, 10.3901806 -1.9615705, 10.76536686 -1.8477590, 11.11114046 -1.66293922, 11.41421356 -1.41421356, 11.66293922 -1.11114046, 11.84775906 -0.76536686, 11.96157056 -0.3901806, 12 0, 12 10)",
         -2, 1, GEOSBUF_JOIN_ROUND, 2,
         0.000001
         );
@@ -132,7 +132,7 @@ void object::test<5>()
         "LINESTRING(33282908 6005055,33282900 6005050,33282892 6005042,33282876 6005007,33282863 6004982,33282866 6004971,33282876 6004975,33282967 6005018,33282999 6005031)",
         // Old algorithm
         // "LINESTRING EMPTY",
-        "LINESTRING (33282939.63869393 6005053.735950421, 33282948.754269257 6005058.043310191, 33282949.873293087 6005058.534544423, 33282982.439409934 6005071.764529393)",
+        "LINESTRING (33282951.601378817 6005059.236579252, 33282982.439409934 6005071.764529393)",
         44, 1, GEOSBUF_JOIN_MITRE, 1,
         0.000001
         );

diff --git a/tests/unit/operation/buffer/OffsetCurveTest.cpp b/tests/unit/operation/buffer/OffsetCurveTest.cpp
@@ -525,7 +525,7 @@ void object::test<38> ()
     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)"
+        "LINESTRING (12.928932188134524 27.071067811865476, 42.928932188134524 57.071067811865476, 44.44429766980398 58.314696123025456, 46.1731656763491 59.23879532511287, 48.04909677983872 59.80785280403231, 50 60, 51.95090322016128 59.80785280403231, 53.8268343236509 59.23879532511287, 55.55570233019602 58.314696123025456, 57.071067811865476 57.071067811865476, 87.07106781186548 27.071067811865476)"
         );
 }
 
@@ -554,5 +554,32 @@ void object::test<40> ()
 }
 
 
+// testMinQuadrantSegments
+// See https://github.com/qgis/QGIS/issues/53165
+template<>
+template<>
+void object::test<41> ()
+{
+    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)"
+    );
+}
+
+// testMinQuadrantSegments_QGIS
+// See https://github.com/qgis/QGIS/issues/53165#issuecomment-1563214857
+template<>
+template<>
+void object::test<42> ()
+{
+    checkOffsetCurve(
+        "LINESTRING (421 622, 446 625, 449 627)",
+        133, 0, BufferParameters::JOIN_MITRE, -1,
+        "LINESTRING (405.15 754.05, 416.3 755.39)"
+    );
+}
+
+
 
 } // namespace tut
diff --git a/web/content/specifications/geojson.md b/web/content/specifications/geojson.md
@@ -14,7 +14,7 @@ Unlike [WKB]({{< ref "wkb" >}}) and [WKT]({{< ref "wkt" >}}), GeoJSON does not r
 * [Feature](https://datatracker.ietf.org/doc/html/rfc7946#section-3.2), representation of an object that has a "geometry" and an arbitrary set of other non-geometric "properties".
 * [FeatureCollection](https://datatracker.ietf.org/doc/html/rfc7946#section-3.3), representation of a list of Features.
 
-Since GEOS is almost 100% concerned with geometry operations, there is no GEOS abstraction to translate the non-geometric properties of GeoJSON Feature into, so handling of Feature properties is only available via the C++ [GeoJSON.h](/libgeos/geos/blob/main/include/geos/io/GeoJSON.h) utilities.
+Since GEOS is almost 100% concerned with geometry operations, there is no GEOS abstraction to translate the non-geometric properties of GeoJSON Feature into, so handling of Feature properties is only available via the C++ [GeoJSON.h](https://github.com/libgeos/geos/blob/main/include/geos/io/GeoJSON.h) utilities.
 
 
 ### Writing GeoJSON