@spec bounds(t()) :: [number()]

Returns the projection's visible bounds as [x0, y0, x1, y1]

@spec center(t(), number(), number()) :: t()

Sets the center point (longitude, latitude)

@spec clip_angle(t(), number() | nil) :: t()

Sets the clip angle for azimuthal projections (in degrees)

@spec fit(t(), [[number()]], [{number(), number()}]) :: t()

Fits the projection to a list of {lon, lat} points (spec/07 §1.6, #475): d3-geo's fitExtent over points.

The points are projected at scale 150 and translate {0, 0}, and scale and translate are set so their projected bounds fill the pixel box [[x0, y0], [x1, y1]] on the tighter axis and are centred in it. center, rotate, clip_angle and parallels are untouched, so a Mercator projection stays Web-Mercator. An axis along which the points have no extent does not bound the scale; with no extent on either the scale is kept and the point is centred; with no projectable point the projection is returned unchanged.

Examples

iex> proj =
...>   Visualize.Geo.Projection.new(:mercator)
...>   |> Visualize.Geo.Projection.fit([[0, 0], [100, 100]], [{-10, 0}, {10, 0}])
iex> {x0, _} = Visualize.Geo.Projection.project(proj, -10, 0)
iex> {x1, _} = Visualize.Geo.Projection.project(proj, 10, 0)
iex> {Float.round(x0, 6), Float.round(x1, 6), proj.center}
{0.0, 100.0, {0, 0}}

@spec fit_extent(t(), [[number()]], [[number()]]) :: t()

Fits the projection to the specified extent for the given GeoJSON bounds.

extent is [[x0, y0], [x1, y1]] in pixels bounds is [[lon0, lat0], [lon1, lat1]] in degrees

@spec invert(t(), number(), number()) :: {float(), float()} | nil

Inverse projection: converts pixel coordinates (x, y) to geographic (lon, lat).

@spec new(projection_type()) :: t()

Creates a new projection of the specified type

@spec parallels(t(), number(), number()) :: t()

Sets the standard parallels for conic projections

@spec precision(t(), number()) :: t()

Sets the precision (spec/07 §1.1): 0 draws the edge a path is clipped along as d3-geo does at precision(0), its interpolation points joined by straight segments; any other value samples that edge every degree (§2.2).

@spec project(t(), number(), number()) :: {float(), float()} | nil

Projects a geographic point (longitude, latitude) to pixel coordinates (x, y).

@spec rotate(t(), number(), number(), number()) :: t()

Sets the rotation (lambda, phi, gamma), in degrees: d3-geo's projection.rotate at [-lambda, phi, gamma] (spec/07 §1.4).

• lambda: the central meridian — the longitude turned to the centre (d3's λ with the opposite sign)
• phi: d3's φ, a tilt toward or away from the viewer — -20 brings 20° N to the centre of an azimuthal view
• gamma: d3's γ, a roll about the viewing axis

@spec scale(t(), number()) :: t()

Sets the scale factor

@spec sphere(t()) :: [{float(), float()}]

The projection's outline as a closed list of {x, y} pixel points (spec/07 §1.6): the sphere of d3-geo's {type: "Sphere"}.

With a clip_angle it is the small circle at that angular distance from the centre, taken in the rotated and centred frame so rotate and center turn the globe under it, at 360 bearings and projected without the clip test; without one it is the map's edge — the antimeridian on either side and the two poles, sampled every degree, at latitude ±85 for the Mercators and ±90 otherwise. A point the raw projection cannot place is dropped.

@spec translate(t(), number(), number()) :: t()

Sets the translation offset