Add ConcaveHull from geos lib (#598)

peterstace · Apr 5, 2024 · db33b8c · db33b8c
1 parent c6d26e9
commit db33b8c
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Showing 2 changed files with 33 additions and 0 deletions.
diff --git a/geos/entrypoints.go b/geos/entrypoints.go
@@ -286,3 +286,10 @@ func CoverageUnion(g geom.Geometry) (geom.Geometry, error) {
 func UnaryUnion(g geom.Geometry) (geom.Geometry, error) {
 	return rawgeos.UnaryUnion(g)
 }
+
+// ConcaveHull returns concave hull of input geometry.
+// concavenessRatio - ratio 0 to 1 (0 - max concaveness, 1 - convex hull)
+// allowHoles - true to allow holes inside of polygons.
+func ConcaveHull(g geom.Geometry, concavenessRatio float64, allowHoles bool) (geom.Geometry, error) {
+	return rawgeos.ConcaveHull(g, concavenessRatio, allowHoles)
+}
diff --git a/internal/rawgeos/entrypoints.go b/internal/rawgeos/entrypoints.go
@@ -26,6 +26,16 @@ GEOSGeometry *GEOSMakeValid_r(GEOSContextHandle_t handle, const GEOSGeometry* g)
 GEOSGeometry *GEOSCoverageUnion_r(GEOSContextHandle_t handle, const GEOSGeometry* g) { return NULL; }
 #endif
 
+#define CONCAVE_HULL_MIN_VERSION "3.11.0"
+#define CONCAVE_HULL_MISSING ( \
+	GEOS_VERSION_MAJOR < 3 || \
+	(GEOS_VERSION_MAJOR == 3 && GEOS_VERSION_MINOR < 11) \
+)
+#if CONCAVE_HULL_MISSING
+// This stub implementation always fails:
+GEOSGeometry* GEOSConcaveHull_r(GEOSContextHandle_t handle, const GEOSGeometry *g, double ratio, unsigned int allowHoles) { return NULL; }
+#endif
+
 */
 import "C"
 
@@ -356,6 +366,22 @@ func ConvexHull(g geom.Geometry) (geom.Geometry, error) {
 	return result, wrap(err, "executing GEOSConvexHull_r")
 }
 
+func ConcaveHull(g geom.Geometry, pctconvex float64, allowHoles bool) (geom.Geometry, error) {
+	if C.CONCAVE_HULL_MISSING != 0 {
+		return geom.Geometry{}, unsupportedGEOSVersionError{
+			C.CONCAVE_HULL_MIN_VERSION, "ConcaveHull",
+		}
+	}
+	result, err := unaryOpG(g, func(ctx C.GEOSContextHandle_t, g *C.GEOSGeometry) *C.GEOSGeometry {
+		ah := C.uint(0)
+		if allowHoles {
+			ah = 1
+		}
+		return C.GEOSConcaveHull_r(ctx, g, C.double(pctconvex), ah)
+	})
+	return result, wrap(err, "executing GEOSConcaveHull_r")
+}
+
 func Centroid(g geom.Geometry) (geom.Geometry, error) {
 	result, err := unaryOpG(g, func(ctx C.GEOSContextHandle_t, g *C.GEOSGeometry) *C.GEOSGeometry {
 		return C.GEOSGetCentroid_r(ctx, g)