mirror of https://github.com/tidwall/tile38.git
44 lines
1.1 KiB
Go
44 lines
1.1 KiB
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 clipLineString(
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lineString *geojson.LineString, clipper geojson.Object,
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) geojson.Object {
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bbox := clipper.Rect()
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var newPoints [][]geometry.Point
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var clipped geometry.Segment
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var rejected bool
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var line []geometry.Point
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base := lineString.Base()
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nSegments := base.NumSegments()
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for i := 0; i < nSegments; i++ {
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clipped, rejected = clipSegment(base.SegmentAt(i), bbox)
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if rejected {
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continue
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}
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if len(line) > 0 && line[len(line)-1] != clipped.A {
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newPoints = append(newPoints, line)
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line = []geometry.Point{clipped.A}
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} else if len(line) == 0 {
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line = append(line, clipped.A)
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}
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line = append(line, clipped.B)
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}
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if len(line) > 0 {
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newPoints = append(newPoints, line)
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}
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var children []*geometry.Line
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for _, points := range newPoints {
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children = append(children,
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geometry.NewLine(points, geometry.DefaultIndex))
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}
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if len(children) == 1 {
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return geojson.NewLineString(children[0])
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}
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return geojson.NewMultiLineString(children)
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}
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