Both tools could read MapLibre Tiles but only ever wrote Mapbox Vector
Tiles, so there was no way to convert a tileset into MLT, or to keep a
tileset in MLT once it had been through either of them.
Give them the same --output-format, --pretessellate, and
--no-mlt-feature-sort options that tippecanoe has. tile-join writes the
chosen format to mbtiles files, PMTiles archives, and tile directories,
naming directory tiles and the tileset metadata format accordingly, and
tippecanoe-overzoom writes it to its output tile. Either tool will read
whichever format its sources are in regardless of what it is writing.
The output format selection and the MLT encoder options now live in
mlt.cpp, shared by all three tools rather than defined in main.cpp for
tippecanoe alone, along with encode_tile() for encoding a tile in the
selected format. overzoom() takes the format as a parameter, since
tile-join uses it internally to rescale tiles that will be re-encoded
afterward, and those intermediate tiles should stay MVT.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LxhELiLtpUFwrPSWwTYdHG
Tilesets written with --output-format=mlt could not be read back by any of
tippecanoe's own tools, which made MLT a dead end rather than a tile format.
Build the mlt-cpp decoder from the vendored maplibre-tile-spec submodule
alongside the encoder, and convert a decoded MapLibre Tile back into the
equivalent mvt_tile: geometry, feature ids, and property columns. MLT rings
come back explicitly closed, so the repeated final point becomes an MVT
closepath, and the property columns, which are held in an unordered map,
are sorted by name so that the attributes of a decoded tile come out in a
stable order.
Rather than adding an option to each tool, mvt_tile::decode() detects the
encoding and dispatches, so everywhere tippecanoe already reads a vector
tile can read MLT. An MLT tile begins with a varint layer length followed
by a varint layer tag whose only defined value is 1, while an MVT tile is
a protobuf whose only field is the repeated layer field 3, so it begins
with 0x1a followed by a layer length that can never be as short as the one
byte that would be needed to look like an MLT layer tag.
Tile directories also needed a fix: enumerate_dirtiles() recognized .mlt
file names but still recorded .pbf as the extension to read them back
with, so decoding an MLT directory failed to find any of its tiles.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LxhELiLtpUFwrPSWwTYdHG
Integrate the C++ MLT encoder from maplibre-tile-spec as a submodule.
Tiles are encoded by converting the existing mvt_tile to
mlt::Encoder::Layer and calling the encoder library directly.
New CLI flags:
--output-format=mlt Encode tiles as MLT instead of MVT
--pretessellate Pre-triangulate polygons (MLT only)
--no-mlt-feature-sort Disable within-tile Hilbert sorting (MLT only)
MLT tiles use .mlt extension in directory output and format=mlt in
mbtiles metadata. Compression and all existing flags work unchanged.
Claude