libgd-gis moves into serious cartography territory

January 13, 2026

Rivers of Europe and Entre Ríos rendered directly in Ruby

Today marks a major milestone for libgd-gis: we crossed from “experimental map renderer” into a real GIS-grade drawing engine.

Using nothing but Ruby + libgd, we are now able to render continent-scale river networks, provincial hydrology, and complex GeoJSON layers with proper classification, styling, and compositing — no QGIS, no Mapbox, no JavaScript.

Let’s look at what changed.

🌍 Europe — continental hydrology rendered in Ruby

This image shows the full river system of Europe, loaded from Natural Earth GeoJSON and rendered by libgd-gis:

This is not a static tile. This is a live GeoJSON rendering pipeline:

GeoJSON → Feature → Projection → Style → GD raster 

Every river you see is:

• Parsed from GeoJSON
• Classified as water
• Projected to image coordinates
• Drawn with vector-correct stroke geometry
• Composited onto a basemap

In traditional GIS this would require GDAL + QGIS + PostGIS. Here it runs inside a single Ruby process.

🇦🇷 Entre Ríos — real provincial-scale hydrography

The same pipeline now works at regional precision.

This is Entre Ríos Province, Argentina, using hydrology layers only:

Notice what is being rendered:

• Paraná River (main channel)
• Uruguay River
• Delta branches
• Interior streams
• Tributaries and sub-basins

All of this comes from GeoJSON water features, not raster tiles.

🧠 What changed in libgd-gis

The key upgrade today was semantic layer classification.

Instead of blindly drawing everything, libgd-gis now understands what a feature is:

water:
  ign:
    objeto:
      - canal
      - río
      - arroyo
      - embalse
      - laguna
      - dique
      - represa
    gna:
      - canal
      - río
      - arroyo
      - embalse
      - laguna 

This ontology allows libgd-gis to:

• Detect water bodies across datasets
• Merge IGN + GNA + Natural Earth + OSM sources
• Draw them in a unified water layer
• Apply special stroke & fill rules

This is real GIS semantics, not just drawing lines.

🎨 Styles now behave like real map engines

Water is not just “blue lines” anymore.

libgd-gis now supports:

• Multi-stroke rivers
• Center lines
• Width scaling
• Alpha transparency
• Polygon vs line water bodies

Example:

water:
  stroke: [0, 120, 255]
  stroke_width: 6
  fill: [180, 220, 255]
  fill_width: 4
  center: [255, 255, 255]
  center_width: 1 

That is how real cartography is done — and now Ruby can do it.

🗺️ Why this matters

You can now build:

• Hydrology maps
• Environmental dashboards
• Flood modeling previews
• GIS thumbnails
• Offline map images
• Scientific plots
• Spatial reports

…all inside Ruby, without external GIS engines.

This is not about replacing QGIS. This is about embedding GIS inside Ruby applications.

Rails can now generate maps.

🚀 What this unlocks next

Because water, roads, railways, parks, cities and regions are now first-class layers, the next steps become possible:

• Label placement
• Z-ordering
• Symbolizers
• Heatmaps
• Tile generation
• Thematic GIS (population, climate, terrain)

libgd-gis is no longer a toy — it is becoming a Ruby GIS engine.

If you are in the Ruby ecosystem and you ever thought “why do I need JavaScript just to draw a map?”

Now you don’t.

Ruby can draw the world.