Module heightmap 

Heightmap codecs for elevation tile formats.

Two flavours of heightmap encoding are supported:

• RGB tiles (this module, top level): terrarium, mapbox, gsi. Elevations packed into 3-byte (R, G, B) pixels, usually served wrapped in a PNG or WebP container.
• Cesium heightmap-1.0 (cesium): 16-bit little-endian heights plus child-tile mask. Cesium’s legacy terrain format.

The container submodule (behind the image cargo feature) wraps the encoded RGB bytes in PNG or WebP for serving as image tiles.

Three formats are supported, each as a (encode_pixel, decode_pixel, encode, decode) quadruplet:

• terrarium — Mapzen / Tilezen / Stadia “Terrarium” encoding. elevation = (R * 256 + G + B / 256) - 32768
• mapbox — Mapbox “Terrain-RGB” encoding. elevation = -10000 + (R * 65536 + G * 256 + B) * 0.1
• gsi — Geospatial Information Authority of Japan (地理院) signed-integer DEM PNG. (128, 0, 0) is the no-data sentinel (decodes to NaN).

Per-pixel functions (encode_pixel / decode_pixel) convert single samples and are useful for streaming, hot loops, custom layouts, and tests. Bulk encode / decode are thin wrappers that walk row-major width × height buffers.

Unified runtime-dispatch API

When the format is only known at runtime (CLI flag, request param, config file), use the HeightmapFormat enum and the top-level encode_pixel, decode_pixel, encode, decode functions:

use terrain_codec::heightmap::{HeightmapFormat, encode_pixel};
let fmt: HeightmapFormat = "terrarium".parse().unwrap();
let rgb = encode_pixel(fmt, 123.45);

The codecs operate on raw (R, G, B) byte triplets and produce flat row-major buffers, so they’re agnostic to the container format. Wrap the encoded bytes in PNG/WebP yourself (e.g. via the image crate) depending on your service.

Modules

cesium

Cesium heightmap-1.0 terrain tile format.

container

PNG / WebP / AVIF container helpers for heightmap RGB bytes.

gsi

Geospatial Information Authority of Japan (GSI / 国土地理院) DEM tile encoding.

mapbox

Mapbox “Terrain-RGB” elevation tile encoding.

terrarium

Mapzen / Tilezen / Stadia “Terrarium” elevation tile encoding.

Structs

ParseHeightmapFormatError

Error returned by HeightmapFormat::from_str for an unrecognised name.

Enums

HeightmapFormat

Identifies one of the supported RGB heightmap encodings, for runtime-dispatched encode/decode via the top-level functions (encode_pixel, decode_pixel, encode, decode).

Functions

decode

Decode a flat width × height × 3 RGB buffer back to elevations using the chosen format.

decode_pixel

Decode a single (R, G, B) pixel into elevation (metres) using the chosen format.

encode

Encode elevations (metres) into a flat width × height × 3 RGB buffer using the chosen format.

encode_pixel

Encode a single elevation sample (metres) into (R, G, B) using the chosen format.