Initial commit of Incremental Delaunay triangulation

geom.go

@@ -133,3 +133,79 @@ func GetCoordinates(g Geometry) (pts []Point, err error) {
 	err = getCoordinates(g, &pts)
 	return pts, err
 }
+
+// extractLines is a helper function for ExtractLines to avoid too many
+// array copies and still provide a convenient interface to the user.
+func extractLines(g Geometry, lines *[]Line) error {
+	switch gg := g.(type) {
+
+	default:
+
+		return ErrUnknownGeometry
+
+	case Pointer:
+
+		return nil
+
+	case MultiPointer:
+
+		return nil
+
+	case LineStringer:
+
+		v := gg.Verticies()
+		for i := 0; i < len(v) - 1; i++ {
+			*lines = append(*lines, Line{v[i], v[i + 1]})
+		}
+		return nil
+
+	case MultiLineStringer:
+
+		for _, ls := range gg.LineStrings() {
+			if err := extractLines(LineString(ls), lines); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	case Polygoner:
+
+		for _, ls := range gg.LinearRings() {
+			if err := extractLines(LineString(ls), lines); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	case MultiPolygoner:
+
+		for _, p := range gg.Polygons() {
+			if err := extractLines(Polygon(p), lines); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	case Collectioner:
+
+		for _, child := range gg.Geometries() {
+			if err := extractLines(child, lines); err != nil {
+				return err
+			}
+		}
+		return nil
+
+	}
+}
+
+/*
+ExtractLines extracts all linear components from a geometry (line segements). 
+If the geometry contains no line segements (e.g. empty geometry or 
+point), then an empty array will be returned.
+
+Duplicate lines will not be removed.
+*/
+func ExtractLines(g Geometry) (lines []Line, err error) {
+	err = extractLines(g, &lines)
+	return lines, err
+}

geom_test.go

@@ -124,3 +124,122 @@ func TestGetCoordinates(t *testing.T) {
 		t.Run(strconv.FormatInt(int64(i), 10), func(t *testing.T) { fn(t, tc) })
 	}
 }
+
+func TestExtractLines(t *testing.T) {
+
+	type tcase struct {
+		geom     Geometry
+		expected []Line
+		err      error
+	}
+
+	fn := func(t *testing.T, tc tcase) {
+		r, err := ExtractLines(tc.geom)
+		if err != tc.err {
+			t.Errorf("error, expected %v got %v", tc.err, err)
+		}
+		if !(len(r) == 0 && len(tc.expected) == 0) && !reflect.DeepEqual(r, tc.expected) {
+			t.Errorf("error, expected %v got %v", tc.expected, r)
+		}
+	}
+	testcases := []tcase{
+		{
+			geom:     Point{10, 20},
+			expected: []Line{},
+			err:      nil,
+		},
+		{
+			geom: MultiPoint{
+				{10, 20},
+				{30, 40},
+				{-10, -5},
+			},
+			expected: []Line{},
+			err:      nil,
+		},
+		{
+			geom: LineString{
+				{10, 20},
+				{30, 40},
+				{-10, -5},
+			},
+			expected: []Line{{{10, 20}, {30, 40}}, {{30, 40}, {-10, -5}}},
+			err:      nil,
+		},
+		{
+			geom: MultiLineString{
+				{
+					{10, 20},
+					{30, 40},
+				},
+				{
+					{-10, -5},
+					{15, 20},
+				},
+			},
+			expected: []Line{{{10, 20}, {30, 40}}, {{-10, -5}, {15, 20}}},
+			err:      nil,
+		},
+		{
+			geom: Polygon{
+				{
+					{10, 20},
+					{30, 40},
+					{-10, -5},
+				},
+				{
+					{1, 2},
+					{3, 4},
+				},
+			},
+			expected: []Line{{{10, 20}, {30, 40}}, {{30, 40}, {-10, -5}}, {{1, 2}, {3, 4}}},
+			err:      nil,
+		},
+		{
+			geom: MultiPolygon{
+				{
+					{
+						{10, 20},
+						{30, 40},
+						{-10, -5},
+					},
+					{
+						{1, 2},
+						{3, 4},
+					},
+				},
+				{
+					{
+						{5, 6},
+						{7, 8},
+						{9, 10},
+					},
+				},
+			},
+			expected: []Line{{{10, 20}, {30, 40}}, {{30, 40}, {-10, -5}}, {{1, 2}, {3, 4}}, {{5, 6}, {7, 8}}, {{7, 8}, {9, 10}}},
+			err:      nil,
+		},
+		{
+			geom: Collection{
+				Point{10, 20},
+				MultiPoint{
+					{10, 20},
+					{30, 40},
+					{-10, -5},
+				},
+				LineString{
+					{1, 2},
+					{3, 4},
+					{5, 6},
+				},
+			},
+			expected: []Line{{{1, 2}, {3, 4}}, {{3, 4}, {5, 6}}},
+			err:      nil,
+		},
+	}
+
+	for i, tc := range testcases {
+		tc := tc
+		t.Run(strconv.FormatInt(int64(i), 10), func(t *testing.T) { fn(t, tc) })
+	}
+}

planar/algorithm/LICENSE

@@ -0,0 +1,30 @@
+Eclipse Distribution License - v 1.0
+
+Copyright (c) 2007, Eclipse Foundation, Inc. and its licensors.
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+  Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+  Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+  Neither the name of the Eclipse Foundation, Inc. nor the names of its
+  contributors may be used to endorse or promote products derived from this
+  software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.