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package io.data2viz.geo.path
import io.data2viz.geom.Extent
import io.data2viz.geo.projection.Projection
import io.data2viz.geo.projection.identityProjection
import io.data2viz.geo.stream
import io.data2viz.geojson.GeoJsonObject
import io.data2viz.geom.Path
fun geoPath(projection: Projection? = null, context: Path? = null) =
GeoPath(if (projection == null) identityProjection() else projection, context)
/**
* If a projection is specified, sets the current projection to the specified projection.
* If projection is not specified, use the identity transformation: the input geometry is not projected and is instead
* rendered directly in raw coordinates.
* This can be useful for fast rendering of pre-projected geometry, or for fast rendering of the equirectangular
* projection.
*
* The given projection is typically one of built-in geographic projections; however, any object that exposes a
* projection.stream function can be used, enabling the use of custom projections.
*/
class GeoPath(val projection: Projection, val context: Path?) {
private val pathArea = PathArea()
private val pathBounds = PathBounds()
private val pathCentroid = PathCentroid()
private val pathMeasure = PathMeasure()
private val contextStream: PathContext? = if (context != null) PathContext(context) else null
/**
* Renders the given object, which may be any GeoJSON feature or geometry object:
* Point - a single position.
* MultiPoint - an array of positions.
* LineString - an array of positions forming a continuous line.
* MultiLineString - an array of arrays of positions forming several lines.
* Polygon - an array of arrays of positions forming a polygon (possibly with holes).
* MultiPolygon - a multidimensional array of positions forming multiple polygons.
* GeometryCollection - an array of geometry objects.
* Feature - a feature containing one of the above geometry objects.
* FeatureCollection - an array of feature objects.
*
* The type Sphere is also supported, which is useful for rendering the outline of the globe; a sphere has no
* coordinates. Any additional arguments are passed along to the pointRadius accessor.
*
* Separate path elements are typically slower than a single path element.
* However, distinct path elements are useful for styling and interaction (e.g., click or mouseover).
*/
fun path(geo: GeoJsonObject): Path {
requireNotNull(context) { "Cannot use GeoPath.svgPath() without a valid context." }
requireNotNull(contextStream) { "Cannot use GeoPath.svgPath() without a valid context." }
stream(geo, projection.stream(contextStream))
return context
}
/**
* Returns the projected planar centroid (typically in pixels) for the specified GeoJSON object.
* This is handy for, say, labeling state or county boundaries, or displaying a symbol map.
* For example, a noncontiguous cartogram might scale each state around its centroid.
* This method observes any clipping performed by the projection; see projection.clipAngle and projection.clipExtent.
* This is the planar equivalent of GeoCentroid.
*/
fun centroid(geo: GeoJsonObject): DoubleArray {
stream(geo, projection.stream(pathCentroid))
return pathCentroid.result()
}
/**
* Returns the projected planar area (typically in square pixels) for the specified GeoJSON object.
* Point, MultiPoint, LineString and MultiLineString geometries have zero area.
* For Polygon and MultiPolygon geometries, this method first computes the area of the exterior ring, and then
* subtracts the area of any interior holes.
* This method observes any clipping performed by the projection; see projection.clipAngle and projection.clipExtent.
* This is the planar equivalent of GeoArea.
*/
fun area(geo: GeoJsonObject): Double {
stream(geo, projection.stream(pathArea))
return pathArea.result()
}
/**
* Returns the projected planar bounding box (typically in pixels) for the specified GeoJSON object.
* The bounding box is represented by an Extent: (x₀, y₀, x₁, y₁),
* where x₀ is the minimum x-coordinate,
* y₀ is the minimum y-coordinate,
* x₁ is maximum x-coordinate,
* and y₁ is the maximum y-coordinate.
* This is handy for, say, zooming in to a particular feature.
* (Note that in projected planar coordinates, the minimum latitude is typically the maximum y-value, and the
* maximum latitude is typically the minimum y-value.)
* This method observes any clipping performed by the projection; see projection.clipAngle and projection.clipExtent.
* This is the planar equivalent of GeoBounds.
*/
fun bounds(geo: GeoJsonObject): Extent {
stream(geo, projection.stream(pathBounds))
return pathBounds.result()
}
/**
* Returns the projected planar length (typically in pixels) for the specified GeoJSON object.
* Point and MultiPoint geometries have zero length.
* For Polygon and MultiPolygon geometries, this method computes the summed length of all rings.
* This method observes any clipping performed by the projection; see projection.clipAngle and projection.clipExtent.
* This is the planar equivalent of GeoLength.
*/
fun measure(geo: GeoJsonObject): Double {
stream(geo, projection.stream(pathMeasure))
return pathMeasure.result()
}
}
