libgd-gis is a A native map rendering engine for Ruby built on libgd.

It allows developers to generate maps, tiles, and heatmaps directly from GeoJSON using the libgd raster engine — without external services.

libgd-gis is useful for:

• Generating static maps for Rails applications
• Rendering GeoJSON data to PNG images
• Creating heatmaps and geographic visualizations
• Building internal dashboards with map outputs
• Self-hosted alternatives to static map APIs

map = GD::GIS::Map.new(
  bbox: PARIS,
  zoom: 13,
  basemap: :carto_light)

map.add_geojson("countries.geojson")
map.add_point(lat: -34.6, lon: -58.4)
map.render

map.save("map.png")

🆕 Update: Style is no longer mandatory. Maps now render out-of-the-box using a built-in default style.

• Web Mercator map and tile rendering (OSM, CARTO, ESRI, Stamen, etc.)
• CRS normalization (CRS84, EPSG:4326, EPSG:3857, Gauss–Krüger Argentina)
• Layered rendering pipeline
• YAML-based styling
• Rule-based semantic classification (ontology)
• Points, lines, and polygons support
• No heavy GIS dependencies

Add to your Gemfile:

gem "libgd-gis"

Then run:

bundle install

You must also have GD available on your system.

require "gd/gis"

map = GD::GIS::Map.new(
  bbox: [-58.45, -34.7, -58.35, -34.55],
  zoom: 13,
  basemap: :carto_light,
  width: 1024,
  height: 768
)

map.style = GD::GIS::Style.load("default", from: "styles")

map.add_geojson("data/roads.geojson")
map.add_geojson("data/water.geojson")

map.render
map.save("map.png")

require "gd/gis"

map = GD::GIS::Map.new(
  bbox: PARIS,
  zoom: 13,
  basemap: :carto_light
)

map.style = GD::GIS::Style.load("default")

map.render

# styles/default.yml

roads:
  motorway:
    stroke: [255, 255, 255]
    stroke_width: 10
    fill: [60, 60, 60]
    fill_width: 6

  primary:
    stroke: [200, 200, 200]
    stroke_width: 7
    fill: [80, 80, 80]
    fill_width: 4

  street:
    stroke: [120, 120, 120]
    stroke_width: 1

rail:
  stroke: [255, 255, 255]
  stroke_width: 6
  fill: [220, 50, 50]
  fill_width: 4
  center: [255, 255, 255]
  center_width: 1

water:
  fill: [120, 180, 255]
  fill_width: 4
  stroke: [80, 140, 220]

park:
  fill: [40, 80, 40]

order:
  - water
  - park
  - street
  - primary
  - motorway
  - rail

This design ensures predictable rendering and makes all visual decisions explicit and reproducible.

LibGD-GIS includes a global dataset of predefined geographic areas. You can use them directly as the bbox parameter.

map = GD::GIS::Map.new(
  bbox: :argentina,
  zoom: 5,
  width: 800,
  height: 600,
  basemap: :osm
)

You can also use continents or regions:

bbox: :world
bbox: :europe
bbox: :south_america
bbox: :north_america
bbox: :asia

Supported input CRS:

• CRS84
• EPSG:4326
• EPSG:3857
• EPSG:22195 (Gauss–Krüger Argentina, zone 5)

All coordinates are normalized internally to CRS84 (lon, lat).

MIT