mirror of https://github.com/tidwall/tile38.git
73 lines
1.7 KiB
Go
73 lines
1.7 KiB
Go
package geojson
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import (
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"strconv"
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"github.com/tidwall/geojson/geo"
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"github.com/tidwall/geojson/geometry"
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)
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// Circle ...
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type Circle struct {
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Object
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center geometry.Point
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meters float64
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steps int
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km bool
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extra *extra
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}
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// NewCircle returns an circle object
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func NewCircle(center geometry.Point, meters float64, steps int) *Circle {
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if steps < 3 {
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steps = 3
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}
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g := new(Circle)
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g.center = center
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g.meters = meters
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g.steps = steps
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if meters <= 0 {
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g.Object = NewPoint(center)
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} else {
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var points []geometry.Point
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step := 360.0 / float64(steps)
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i := 0
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for deg := 360.0; deg > 0; deg -= step {
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lat, lon := geo.DestinationPoint(center.Y, center.X, meters, deg)
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points = append(points, geometry.Point{X: lon, Y: lat})
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i++
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}
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// TODO: account for the pole and antimerdian. In most cases only a polygon
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// is needed, but when the circle bounds passes the 90/180 lines, we need
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// to create a multipolygon
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points = append(points, points[0])
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g.Object = NewPolygon(
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geometry.NewPoly(points, nil, geometry.DefaultIndex),
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)
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}
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return g
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}
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// AppendJSON ...
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func (g *Circle) AppendJSON(dst []byte) []byte {
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dst = append(dst, `{"type":"Feature","geometry":`...)
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dst = append(dst, `{"type":"Point","coordinates":[`...)
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dst = strconv.AppendFloat(dst, g.center.X, 'f', -1, 64)
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dst = append(dst, ',')
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dst = strconv.AppendFloat(dst, g.center.Y, 'f', -1, 64)
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dst = append(dst, `]},"properties":{"type":"Circle","radius":`...)
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dst = strconv.AppendFloat(dst, g.meters, 'f', -1, 64)
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dst = append(dst, `,"radius_units":"m"}}`...)
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return dst
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}
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// JSON ...
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func (g *Circle) JSON() string {
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return string(g.AppendJSON(nil))
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}
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// String ...
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func (g *Circle) String() string {
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return string(g.AppendJSON(nil))
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}
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