Append bounds method

geos/geom.go

@@ -846,6 +846,56 @@ func (g *Geometry) RelatePat(other *Geometry, pat string) (bool, error) {
 	return boolFromC("RelatePat", cGEOSRelatePattern(g.g, other.g, cs))
 }
 
+type Bounds struct {
+	MinX float64
+	MinY float64
+	MaxX float64
+	MaxY float64
+}
+
+var NilBounds = Bounds{1e20, 1e20, -1e20, -1e20}
+
+// Bounds returns (minx, miny, maxx, maxy) that bounds the object.
+func (g *Geometry) Bounds() (Bounds, error) {
+	geom, err := g.Envelope()
+	if err != nil {
+		return NilBounds, Error()
+	}
+
+	s, err := geom.Shell()
+	if err != nil {
+		return NilBounds, Error()
+	}
+	c, err := s.Coords()
+	if err != nil {
+		return NilBounds, Error()
+	}
+
+	minx := 1.e+20
+	maxx := -1e+20
+	miny := 1.e+20
+	maxy := -1e+20
+
+	for _, cd := range c {
+		if cd.X < minx {
+			minx = cd.X
+		}
+		if cd.X > maxx {
+			maxx = cd.X
+		}
+
+		if cd.Y < miny {
+			miny = cd.Y
+		}
+		if cd.Y > maxy {
+			maxy = cd.Y
+		}
+	}
+
+	return Bounds{minx, miny, maxx, maxy}, nil
+}
+
+
 // various wrappers around C API
 
 type unaryTopo func(*C.GEOSGeometry) *C.GEOSGeometry

geos/geom_test.go

@@ -1063,3 +1063,21 @@ func TestLineInterpolatePoint(t *testing.T) {
 		}
 	}
 }
+
+func TestBounds(t *testing.T) {
+	testPolygon := "POLYGON((17672.0337 9338.1706,17685.6852 9298.5111,17749.098 9319.1397,17742.66 9339.25,17738.74 9342.61,17735.94 9342.4,17732.42 9340.1,17731.2 9340.32,17729.03 9341.35,17720.35 9348.95,17716.3509 9352.6934,17672.0337 9338.1706))"
+	exampleBounds := Bounds{MinX: 17672.0337, MinY: 9298.5111, MaxX: 17749.098, MaxY: 9352.6934}
+	p, err := FromWKT(testPolygon)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bt, err := p.Bounds()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if bt != exampleBounds {
+		t.Errorf("Bounds are not equal %v != %v", bt, exampleBounds)
+	}
+}