[go: up one dir, main page]

geo 0.4.1

Geospatial primitives and algorithms
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216

use num_traits::{Float, FromPrimitive};

use types::{Point, LineString, Polygon, MultiPolygon, Bbox};
use algorithm::area::Area;
use algorithm::distance::Distance;

/// Calculation of the centroid.
pub trait Centroid<T: Float> {
    /// Calculation the centroid, see: https://en.wikipedia.org/wiki/Centroid
    ///
    /// ```
    /// use geo::{Point, LineString, Coordinate};
    /// use geo::algorithm::centroid::Centroid;
    ///
    /// let mut vec = Vec::new();
    /// vec.push(Point::new(40.02f64, 116.34));
    /// vec.push(Point::new(40.02f64, 116.34));
    /// let linestring = LineString(vec);
    ///
    /// println!("Centroid {:?}", linestring.centroid());
    /// ```
    ///
    fn centroid(&self) -> Option<Point<T>>;
}

impl<T> Centroid<T> for LineString<T>
    where T: Float
{
    ///
    /// Centroid on a LineString is the mean of the middle of the segment
    /// weighted by the length of the segments.
    ///
    fn centroid(&self) -> Option<Point<T>> {
        let vect = &self.0;
        if vect.is_empty() {
            return None;
        }
        if vect.len() == 1 {
            Some(Point::new(vect[0].x(),
                            vect[0].y()))
        } else {
            let mut sum_x = T::zero();
            let mut sum_y = T::zero();
            let mut total_length = T::zero();
            for ps in vect.windows(2) {
                let segment_len = ps[0].distance(&ps[1]);
                let (x1, y1, x2, y2) = (ps[0].x(), ps[0].y(), ps[1].x(), ps[1].y());
                total_length = total_length + segment_len;
                sum_x = sum_x + segment_len * ((x1 + x2) / (T::one() + T::one()));
                sum_y = sum_y + segment_len * ((y1 + y2) / (T::one() + T::one()));
            }
            Some(Point::new(sum_x / total_length, sum_y / total_length))
        }
    }
}

impl<T> Centroid<T> for Polygon<T>
    where T: Float + FromPrimitive
{
    ///
    /// Centroid on a Polygon.
    /// See: https://en.wikipedia.org/wiki/Centroid
    ///
    fn centroid(&self) -> Option<Point<T>> {
        // TODO: consideration of inner polygons;
        let linestring = &self.exterior;
        let vect = &linestring.0;
        if vect.is_empty() {
            return None;
        }
        if vect.len() == 1 {
            Some(Point::new(vect[0].x(), vect[0].y()))
        } else {
            let area = self.area();
            let mut sum_x = T::zero();
            let mut sum_y = T::zero();
            for ps in vect.windows(2) {
                let tmp = ps[0].x() * ps[1].y() - ps[1].x() * ps[0].y();
                sum_x = sum_x + ((ps[1].x() + ps[0].x()) * tmp);
                sum_y = sum_y + ((ps[1].y() + ps[0].y()) * tmp);
            }
            let six = T::from_i32(6).unwrap();
            Some(Point::new(sum_x / (six * area), sum_y / (six * area)))
        }
    }
}

impl<T> Centroid<T> for MultiPolygon<T>
    where T: Float + FromPrimitive
{
    // See: https://fotino.me/calculating-centroids/
    fn centroid(&self) -> Option<Point<T>> {
        let mut sum_x = T::zero();
        let mut sum_y = T::zero();
        let mut total_area = T::zero();
        let vect = &self.0;
        if vect.is_empty() {
            return None;
        }
        for poly in &self.0 {
            // the area is signed
            let area = poly.area().abs();
            total_area = total_area + area;
            if let Some(p) = poly.centroid() {
                sum_x = sum_x + area * p.x();
                sum_y = sum_y + area * p.y();
            }
        }
        Some(Point::new(sum_x / total_area, sum_y / total_area))
    }
}

impl<T> Centroid<T> for Bbox<T>
    where T: Float
{
    ///
    /// Centroid on a Bbox.
    ///
    fn centroid(&self) -> Option<Point<T>> {
        let two = T::one() + T::one();
        Some(Point::new((self.xmax + self.xmin)/two, (self.ymax + self.ymin)/two))
    }
}

#[cfg(test)]
mod test {
    use types::{COORD_PRECISION, Coordinate, Point, LineString, Polygon, MultiPolygon, Bbox};
    use algorithm::centroid::Centroid;
    use algorithm::distance::Distance;
    /// Tests: Centroid of LineString
    #[test]
    fn empty_linestring_test() {
        let vec = Vec::<Point<f64>>::new();
        let linestring = LineString(vec);
        let centroid = linestring.centroid();
        assert!(centroid.is_none());
    }
    #[test]
    fn linestring_one_point_test() {
        let p = Point::new(40.02f64, 116.34);
        let mut vect = Vec::<Point<f64>>::new();
        vect.push(p);
        let linestring = LineString(vect);
        let centroid = linestring.centroid();
        assert_eq!(centroid, Some(p));
    }
    #[test]
    fn linestring_test() {
        let p = |x| Point(Coordinate { x: x, y: 1. });
        let linestring = LineString(vec![p(1.), p(7.), p(8.), p(9.), p(10.), p(11.)]);
        assert_eq!(linestring.centroid(),
                   Some(Point(Coordinate { x: 6., y: 1. })));
    }
    /// Tests: Centroid of Polygon
    #[test]
    fn empty_polygon_test() {
        let v1 = Vec::new();
        let v2 = Vec::new();
        let linestring = LineString::<f64>(v1);
        let poly = Polygon::new(linestring, v2);
        assert!(poly.centroid().is_none());
    }
    #[test]
    fn polygon_one_point_test() {
        let p = Point(Coordinate { x: 2., y: 1. });
        let v = Vec::new();
        let linestring = LineString(vec![p]);
        let poly = Polygon::new(linestring, v);
        assert_eq!(poly.centroid(), Some(p));
    }
    #[test]
    fn polygon_test() {
        let p = |x, y| Point(Coordinate { x: x, y: y });
        let v = Vec::new();
        let linestring = LineString(vec![p(0., 0.), p(2., 0.), p(2., 2.), p(0., 2.), p(0., 0.)]);
        let poly = Polygon::new(linestring, v);
        assert_eq!(poly.centroid(), Some(p(1., 1.)));
    }
    /// Tests: Centroid of MultiPolygon
    #[test]
    fn empty_multipolygon_polygon_test() {
        assert!(MultiPolygon::<f64>(Vec::new()).centroid().is_none());
    }
    #[test]
    fn multipolygon_one_polygon_test() {
        let p = |x, y| Point(Coordinate { x: x, y: y });
        let linestring = LineString(vec![p(0., 0.), p(2., 0.), p(2., 2.), p(0., 2.), p(0., 0.)]);
        let poly = Polygon::new(linestring, Vec::new());
        assert_eq!(MultiPolygon(vec![poly]).centroid(), Some(p(1., 1.)));
    }
    #[test]
    fn multipolygon_two_polygons_test() {
        let p = |x, y| Point(Coordinate { x: x, y: y });
        let linestring = LineString(vec![p(2., 1.), p(5., 1.), p(5., 3.), p(2., 3.), p(2., 1.)]);
        let poly1 = Polygon::new(linestring, Vec::new());
        let linestring = LineString(vec![p(7., 1.), p(8., 1.), p(8., 2.), p(7., 2.), p(7., 1.)]);
        let poly2 = Polygon::new(linestring, Vec::new());
        let dist = MultiPolygon(vec![poly1, poly2]).centroid().unwrap().distance(&p(4.07142857142857, 1.92857142857143));
        assert!(dist < COORD_PRECISION);
    }
    #[test]
    fn multipolygon_two_polygons_of_opposite_clockwise_test() {
        let p = |x, y| Point(Coordinate { x: x, y: y });
        let linestring = LineString(vec![p(0., 0.), p(2., 0.), p(2., 2.), p(0., 2.), p(0., 0.)]);
        let poly1 = Polygon::new(linestring, Vec::new());
        let linestring = LineString(vec![p(0., 0.), p(-2., 0.), p(-2., 2.), p(0., 2.), p(0., 0.)]);
        let poly2 = Polygon::new(linestring, Vec::new());
        assert_eq!(MultiPolygon(vec![poly1, poly2]).centroid(), Some(p(0., 1.)));
    }
    #[test]
    fn bbox_test() {
        let bbox = Bbox{ xmax: 4., xmin: 0., ymax: 100., ymin: 50.};
        let point = Point(Coordinate { x: 2., y: 75. });
        assert_eq!(point, bbox.centroid().unwrap());
    }
}