72 lines
1.2 KiB
Go
72 lines
1.2 KiB
Go
package length
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import (
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"fmt"
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"github.com/paulmach/orb"
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)
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// Length returns the length of the boundary of the geometry
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// using 2d euclidean geometry.
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func Length(g orb.Geometry, df orb.DistanceFunc) float64 {
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if g == nil {
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return 0
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}
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switch g := g.(type) {
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case orb.Point:
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return 0
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case orb.MultiPoint:
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return 0
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case orb.LineString:
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return lineStringLength(g, df)
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case orb.MultiLineString:
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sum := 0.0
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for _, ls := range g {
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sum += lineStringLength(ls, df)
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}
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return sum
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case orb.Ring:
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return lineStringLength(orb.LineString(g), df)
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case orb.Polygon:
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return polygonLength(g, df)
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case orb.MultiPolygon:
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sum := 0.0
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for _, p := range g {
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sum += polygonLength(p, df)
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}
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return sum
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case orb.Collection:
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sum := 0.0
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for _, c := range g {
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sum += Length(c, df)
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}
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return sum
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case orb.Bound:
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return Length(g.ToRing(), df)
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}
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panic(fmt.Sprintf("geometry type not supported: %T", g))
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}
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func lineStringLength(ls orb.LineString, df orb.DistanceFunc) float64 {
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sum := 0.0
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for i := 1; i < len(ls); i++ {
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sum += df(ls[i], ls[i-1])
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}
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return sum
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}
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func polygonLength(p orb.Polygon, df orb.DistanceFunc) float64 {
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sum := 0.0
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for _, r := range p {
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sum += lineStringLength(orb.LineString(r), df)
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}
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return sum
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}
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