nodes and output

"nodes": {
  "bg":  { "op": "solid", "color": "#fbf6e6" },
  "out": { "op": "blur", "input": "@bg", "sigma": 2 }
},
"output": "@out"

Node syntax

Each entry is id: { "op": "<op-name>", …fields }. The id is yours; the op name selects the implementation from the registry (all 82 are in the node catalog); everything else is that op’s fields.

Ids may contain letters, digits, _ and -, and must not start with a digit. Function expansion produces ids of the form <call>/<node>, so avoid / in ids you write yourself.

The order of entries is meaningless. Evaluation order comes from the references. Group and name nodes for a human reader.

Wiring

A field whose value is "@other" is a connection. What kind of connection it is depends on the field:

"features": "@water_f"     // a Features port
"input":    "@bg"          // a Raster (or Sprite) port
"brush":    "@pencil"       // a Brush port
"sigma":    "@computed"     // a Scalar port

The op declares each port’s accepted kinds, and build_graph checks them — see ports and types. A numeric field usually accepts a literal, $param, or @node interchangeably.

Fan-out is free and encouraged: several consumers may reference one node, and it is evaluated once because the cache is content-addressed.

Common shapes

A layer. Data always enters through a features node, which is where the filter and zoom gates live, and is shared by every consumer of that layer:

"roads_f": { "op": "features", "layer": "roads",
             "filter-expr": ["==", ["get", "kind"], "highway"],
             "min-zoom": 8 },
"roads":   { "op": "stroke", "features": "@roads_f", "color": "#333", "width-px": 1.5 }

Stacking. Compositing is a blend chain — painter’s algorithm as a graph. ezu translate emits exactly this from a MapLibre layer list:

"c1":  { "op": "blend", "base": "@bg",  "over": "@landuse" },
"c2":  { "op": "blend", "base": "@c1",  "over": "@water" },
"out": { "op": "blend", "base": "@c2",  "over": "@roads" }

For many layers at once, stack composites a list in one node.

Three layers stacked as a blend chain — the shape ezu translate emits from an ordered MapLibre layer list.

Masking. blend with clip: true clips the result to the base’s alpha — Photoshop’s clipping mask, and how a fill-pattern gets confined to its polygon.

Toggling a branch. switch selects between two inputs, which is how --keep-hidden preserves a hidden MapLibre layer without drawing it.

The output

"output": "@out"

output must resolve to a node whose kind is Raster. Notably:

• A Sprite cannot be the output (it is not canvas-sized) — put it through a placement op first.
• Features, Brush, Scalar, Labels and ScalarField cannot be the output either. color-ramp is the usual way to turn a ScalarField into a Raster.

Nodes not reachable from output are still validated but never evaluated — handy for commenting a branch out, cheap to leave in place.

Inspecting a graph

ezu graph style.json     # Mermaid `graph LR` of the dependencies
ezu --verbose tile …      # per-node op, cache hit/miss, output shape, duration

The Mermaid diagram is the fastest way into a translated recipe you did not write.