fixed dependencies

vendor/github.com/paulmach/orb/geo/area.go

@@ -0,0 +1,112 @@
+// Package geo computes properties on geometries assuming they are lon/lat data.
+package geo
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/paulmach/orb"
+)
+
+// Area returns the area of the geometry on the earth.
+func Area(g orb.Geometry) float64 {
+	if g == nil {
+		return 0
+	}
+
+	switch g := g.(type) {
+	case orb.Point, orb.MultiPoint, orb.LineString, orb.MultiLineString:
+		return 0
+	case orb.Ring:
+		return math.Abs(ringArea(g))
+	case orb.Polygon:
+		return polygonArea(g)
+	case orb.MultiPolygon:
+		return multiPolygonArea(g)
+	case orb.Collection:
+		return collectionArea(g)
+	case orb.Bound:
+		return Area(g.ToRing())
+	}
+
+	panic(fmt.Sprintf("geometry type not supported: %T", g))
+}
+
+// SignedArea will return the signed area of the ring.
+// Will return negative if the ring is in the clockwise direction.
+// Will implicitly close the ring.
+func SignedArea(r orb.Ring) float64 {
+	return ringArea(r)
+}
+
+func ringArea(r orb.Ring) float64 {
+	if len(r) < 3 {
+		return 0
+	}
+	var lo, mi, hi int
+
+	l := len(r)
+	if r[0] != r[len(r)-1] {
+		// if not a closed ring, add an implicit calc for that last point.
+		l++
+	}
+
+	// To support implicit closing of ring, replace references to
+	// the last point in r to the first 1.
+
+	area := 0.0
+	for i := 0; i < l; i++ {
+		if i == l-3 { // i = N-3
+			lo = l - 3
+			mi = l - 2
+			hi = 0
+		} else if i == l-2 { // i = N-2
+			lo = l - 2
+			mi = 0
+			hi = 0
+		} else if i == l-1 { // i = N-1
+			lo = 0
+			mi = 0
+			hi = 1
+		} else { // i = 0 to N-3
+			lo = i
+			mi = i + 1
+			hi = i + 2
+		}
+
+		area += (deg2rad(r[hi][0]) - deg2rad(r[lo][0])) * math.Sin(deg2rad(r[mi][1]))
+	}
+
+	return -area * orb.EarthRadius * orb.EarthRadius / 2
+}
+
+func polygonArea(p orb.Polygon) float64 {
+	if len(p) == 0 {
+		return 0
+	}
+
+	sum := math.Abs(ringArea(p[0]))
+	for i := 1; i < len(p); i++ {
+		sum -= math.Abs(ringArea(p[i]))
+	}
+
+	return sum
+}
+
+func multiPolygonArea(mp orb.MultiPolygon) float64 {
+	sum := 0.0
+	for _, p := range mp {
+		sum += polygonArea(p)
+	}
+
+	return sum
+}
+
+func collectionArea(c orb.Collection) float64 {
+	area := 0.0
+	for _, g := range c {
+		area += Area(g)
+	}
+
+	return area
+}