6257ddba78
The big change is that the GeoJSON package has been completely rewritten to fix a few of geometry calculation bugs, increase performance, and to better follow the GeoJSON spec RFC 7946. GeoJSON updates - A LineString now requires at least two points. - All json members, even foreign, now persist with the object. - The bbox member persists too but is no longer used for geometry calculations. This is change in behavior. Previously Tile38 would treat the bbox as the object's physical rectangle. - Corrections to geometry intersects and within calculations. Faster spatial queries - The performance of Point-in-polygon and object intersect operations are greatly improved for complex polygons and line strings. It went from O(n) to roughly O(log n). - The same for all collection types with many children, including FeatureCollection, GeometryCollection, MultiPoint, MultiLineString, and MultiPolygon. Codebase changes - The pkg directory has been renamed to internal - The GeoJSON internal package has been moved to a seperate repo at https://github.com/tidwall/geojson. It's now vendored. Please look out for higher memory usage for datasets using complex shapes. A complex shape is one that has 64 or more points. For these shapes it's expected that there will be increase of least 54 bytes per point.
40 lines
918 B
Go
40 lines
918 B
Go
package clip
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import (
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"github.com/tidwall/geojson"
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"github.com/tidwall/geojson/geometry"
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)
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func clipPolygon(
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polygon *geojson.Polygon, clipper geojson.Object,
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) geojson.Object {
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rect := clipper.Rect()
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var newPoints [][]geometry.Point
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base := polygon.Base()
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rings := []geometry.Ring{base.Exterior}
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rings = append(rings, base.Holes...)
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for _, ring := range rings {
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ringPoints := make([]geometry.Point, ring.NumPoints())
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for i := 0; i < len(ringPoints); i++ {
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ringPoints[i] = ring.PointAt(i)
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}
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newPoints = append(newPoints, clipRing(ringPoints, rect))
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}
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var exterior []geometry.Point
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var holes [][]geometry.Point
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if len(newPoints) > 0 {
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exterior = newPoints[0]
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}
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if len(newPoints) > 1 {
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holes = newPoints[1:]
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}
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newPoly := geojson.NewPolygon(
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geometry.NewPoly(exterior, holes, geometry.DefaultIndex),
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)
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if newPoly.Empty() {
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return geojson.NewMultiPolygon(nil)
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}
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return polygon
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}
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