libgd-gis
add_lines — Custom Line Rendering
The add_lines method allows you to draw custom line overlays on a map using
geographic coordinates, without requiring a GeoJSON file.
It is suitable for routes, paths, tracks, and any linear geometry generated at runtime.
Basic usage
require "gd/gis"
CITY = [-74.05, 40.70, -73.95, 40.80]
map = GD::GIS::Map.new(
bbox: CITY,
zoom: 10,
basemap: :carto_light,
width: 800,
height: 800
)
map.style = GD::GIS::Style.load("light")
Line definition
Lines are defined as an array of line strings, where each line is an array of
[lng, lat] coordinate pairs.
lines = [
[
[-74.02, 40.71],
[-74.00, 40.73],
[-73.98, 40.75]
]
]
Notes
- Coordinates must be in
[lng, lat]order - Lines do not need to be closed
- Multiple lines are supported in a single call
Adding lines to the map
map.add_lines(
lines,
stroke: [239, 68, 68],
width: 3
)
Parameters
lines (required)
Array of line strings defined by geographic coordinates.
stroke
stroke: [R, G, B]
Defines the line color.
width
width: 3
Line width in pixels.
Rendering and saving
map.render
map.save("output/lines.png")
Style interaction
add_lines does not rely on YAML styles.
- Styling is defined inline
- Ideal for dynamic overlays (routes, tracks)
- Fully compatible with global map styles
Summary
- Draw lines without GeoJSON
- Uses
[lng, lat]coordinates - Supports multiple lines
- Independent from YAML style system