PolygonLayer

Screenshot from Overture Maps example

lonboard.PolygonLayer

Bases: BaseArrowLayer

The PolygonLayer renders filled, stroked and/or extruded polygons.

Note

This layer is essentially a combination of a PathLayer and a SolidPolygonLayer. This has some overhead beyond a SolidPolygonLayer, so if you're looking for the maximum performance with large data, you may want to use a SolidPolygonLayer directly.

Example:

From GeoPandas:

import geopandas as gpd
from lonboard import Map, PolygonLayer

# A GeoDataFrame with Polygon or MultiPolygon geometries
gdf = gpd.GeoDataFrame()
layer = PolygonLayer.from_geopandas(
    gdf,
    get_fill_color=[255, 0, 0],
    get_line_color=[0, 100, 100, 150],
)
m = Map(layer)

From geoarrow-rust:

from geoarrow.rust.core import read_parquet
from lonboard import Map, PolygonLayer

# Example: A GeoParquet file with Polygon or MultiPolygon geometries
table = read_parquet("path/to/file.parquet")
layer = PolygonLayer(
    table=table,
    get_fill_color=[255, 0, 0],
    get_line_color=[0, 100, 100, 150],
)
m = Map(layer)

auto_highlight class-attribute instance-attribute

auto_highlight = tag(sync=True)

When true, the current object pointed to by the mouse pointer (when hovered over) is highlighted with highlightColor.

Requires pickable to be True.

• Type: bool
• Default: False

elevation_scale class-attribute instance-attribute

elevation_scale = tag(sync=True)

Elevation multiplier.

The final elevation is calculated by elevationScale * getElevation(d). elevationScale is a handy property to scale all elevation without updating the data.

• Type: float, optional
• Default: 1

extensions class-attribute instance-attribute

extensions = tag(sync=True, **widget_serialization)

A list of layer extension objects to add additional features to a layer.

extruded class-attribute instance-attribute

extruded = tag(sync=True)

Whether to extrude the polygons.

Based on the elevations provided by the getElevation accessor.

If set to false, all polygons will be flat, this generates less geometry and is faster than simply returning 0 from getElevation.

• Type: bool, optional
• Default: False

filled class-attribute instance-attribute

filled = tag(sync=True)

Whether to draw a filled polygon (solid fill).

Note that only the area between the outer polygon and any holes will be filled.

• Type: bool, optional
• Default: True

get_elevation class-attribute instance-attribute

get_elevation = FloatAccessor(None, allow_none=True)

The elevation to extrude each polygon with, in meters.

Only applies if extruded=True.

• Type: FloatAccessor, optional
  • If a number is provided, it is used as the width for all polygons.
  • If an array is provided, each value in the array will be used as the width for the polygon at the same row index.
• Default: 1000.

get_fill_color class-attribute instance-attribute

get_fill_color = ColorAccessor(None, allow_none=True)

The fill color of each polygon in the format of [r, g, b, [a]]. Each channel is a number between 0-255 and a is 255 if not supplied.

• Type: ColorAccessor, optional
  • If a single list or tuple is provided, it is used as the fill color for all polygons.
  • If a numpy or pyarrow array is provided, each value in the array will be used as the fill color for the polygon at the same row index.
• Default: [0, 0, 0, 255].

get_line_color class-attribute instance-attribute

get_line_color = ColorAccessor(None, allow_none=True)

The line color of each polygon in the format of [r, g, b, [a]]. Each channel is a number between 0-255 and a is 255 if not supplied.

Only applies if extruded=True.

• Type: ColorAccessor, optional
  • If a single list or tuple is provided, it is used as the line color for all polygons.
  • If a numpy or pyarrow array is provided, each value in the array will be used as the line color for the polygon at the same row index.
• Default: [0, 0, 0, 255].

get_line_width class-attribute instance-attribute

get_line_width = FloatAccessor(None, allow_none=True)

The width of the outline of each polygon, in units specified by line_width_units (default 'meters').

• Type: FloatAccessor, optional
  • If a number is provided, it is used as the outline width for all polygons.
  • If an array is provided, each value in the array will be used as the outline width for the polygon at the same row index.
• Default: 1.

line_joint_rounded class-attribute instance-attribute

line_joint_rounded = tag(sync=True)

Type of joint. If true, draw round joints. Otherwise draw miter joints.

• Type: bool, optional
• Default: False

line_miter_limit class-attribute instance-attribute

line_miter_limit = tag(sync=True)

The maximum extent of a joint in ratio to the stroke width.

Only works if line_joint_rounded is false.

• Type: float, optional
• Default: 4

line_width_max_pixels class-attribute instance-attribute

line_width_max_pixels = tag(sync=True)

The maximum line width in pixels. This can be used to prevent the line from getting too big when zoomed in.

• Type: float, optional
• Default: None

line_width_min_pixels class-attribute instance-attribute

line_width_min_pixels = tag(sync=True)

The minimum line width in pixels. This can be used to prevent the line from getting too small when zoomed out.

• Type: float, optional
• Default: 0

line_width_scale class-attribute instance-attribute

line_width_scale = tag(sync=True)

The line width multiplier that multiplied to all outlines of Polygon and MultiPolygon features if the stroked attribute is true.

• Type: float, optional
• Default: 1

line_width_units class-attribute instance-attribute

line_width_units = tag(sync=True)

The units of the line width, one of 'meters', 'common', and 'pixels'. See unit system.

• Type: str, optional
• Default: 'meters'

opacity class-attribute instance-attribute

opacity = tag(sync=True)

The opacity of the layer.

• Type: float. Must range between 0 and 1.
• Default: 1

pickable class-attribute instance-attribute

pickable = tag(sync=True)

Whether the layer responds to mouse pointer picking events.

This must be set to True for tooltips and other interactive elements to be available. This can also be used to only allow picking on specific layers within a map instance.

Note that picking has some performance overhead in rendering. To get the absolute best rendering performance with large data (at the cost of removing interactivity), set this to False.

• Type: bool
• Default: True

selected_index class-attribute instance-attribute

selected_index = tag(sync=True)

The positional index of the most-recently clicked on row of data.

You can use this to access the full row of data from a GeoDataFrame

gdf.iloc[layer.selected_index]

Setting a value here from Python will do nothing. This attribute only exists to be updated from JavaScript on a map click. Note that pickable must be True (the default) on this layer for the JavaScript onClick handler to work; if pickable is set to False, selected_index will never update.

Note that you can use observe to call a function whenever a new value is received from JavaScript. Refer here for an example.

stroked class-attribute instance-attribute

stroked = tag(sync=True)

Whether to draw an outline around the polygon (solid fill).

Note that both the outer polygon as well the outlines of any holes will be drawn.

• Type: bool, optional
• Default: True

table class-attribute instance-attribute

table = PyarrowTableTrait(allowed_geometry_types={POLYGON, MULTIPOLYGON})

A GeoArrow table with a Polygon or MultiPolygon column.

This is the fastest way to plot data from an existing GeoArrow source, such as geoarrow-rust or geoarrow-pyarrow.

If you have a GeoPandas GeoDataFrame, use [from_geopandas][lonboard.PolygonLayer.from_geopandas] instead.

visible class-attribute instance-attribute

visible = tag(sync=True)

Whether the layer is visible.

Under most circumstances, using the visible attribute to control the visibility of layers is recommended over removing/adding the layer from the Map.layers list.

In particular, toggling the visible attribute will persist the layer on the JavaScript side, while removing/adding the layer from the Map.layers list will re-download and re-render from scratch.

• Type: bool
• Default: True

wireframe class-attribute instance-attribute

wireframe = tag(sync=True)

Whether to generate a line wireframe of the polygon. The outline will have "horizontal" lines closing the top and bottom polygons and a vertical line (a "strut") for each vertex on the polygon.

• Type: bool, optional
• Default: False

Remarks:

• These lines are rendered with GL.LINE and will thus always be 1 pixel wide.
• Wireframe and solid extrusions are exclusive, you'll need to create two layers with the same data if you want a combined rendering effect.