by Andrew Brampton (bramp.net)
Read PMTiles v3 archives stored locally or remotely.
import 'package:pmtiles/pmtiles.dart';
/// A simple example of reading a PmTiles archive.
Future<int> main() async {
// Open the archive from a file. HTTP URLs are also acceptable.
final archive = await PmTilesArchive.from("/path/to/file.pmtiles");
try {
// # Metadata
// Information about the archive is available in the header and metadata.
print("Header:");
print(archive.header);
// Some interesting fields are also on the main tiles archive object.
print("Type: ${archive.tileType}"); // e.g mvt, png, jpg, etc.
print("Compression: ${archive.tileCompression}"); // e.g gzip, brotli, etc.
// The metadata is a embedded JSON object, as described here:
// https://github.com/protomaps/PMTiles/blob/main/spec/v3/spec.md#5-json-metadata
print("Metadata:");
final prettyJson = JsonEncoder.withIndent(' ') // for clarity pretty print
.convert(await archive.metadata);
print(prettyJson);
// # Tiles
// To extract a tiles from the archive, you index them by a tile ID (which
// can be converted to/from a ZXY coordinate).
final int tileId = ZXY(4, 3, 2).toTileId();
// To extract a single tile:
final Tile t = await archive.tile(tileId);
t.type; // e.g. mvt, png, jpg, etc.
// The uncompressed bytes of the tile is available as a List<int>.
t.bytes();
// Equally if the tile is going to be reserved, you may leave it compressed
// in the format that was used in the archive. See tiles.tileCompression above.
t.compressedBytes();
// To extract multiple tiles:
final tiles = archive.tiles([tileId, tileId + 1, tileId + 2]);
// This returns a Stream<Tiles> and Tiles will be returned as they become
// available from the archive. This is optimised to reduce the requests
// to the archive's backing store, leading to faster extraction.
await for (final tile in tiles) {
print("${tile.id} is available");
// Again the bytes are available via:
tile.bytes();
}
} finally {
// Don't forget the close the archive once you are done.
await archive.close();
}
return 0;
}
Some effort has been made to ensure this library works correctly on the native Dart VM, as well as when dart2js is used to compiled to JavaScript (e.g. for use with Node.js or Chrome). The following table shows the support matrix.
Feature | Dart VM | Node.js | Browsers (e.g Chrome) |
---|---|---|---|
Native | dart2js | dart2js | |
File | Yes | No | No |
HTTP | Yes | No | Yes |
If the library is used in an UnsupportedError exception will be thrown.
Use melos bootstrap
to install dependencies and link packages together.
The package is broken up into three:
-
pmtiles
package contains the core logic and is published to pub.dev. -
pmtiles_cli
is a simple command line tool, mainly used for testing. It is not published to pub.dev. -
pmtiles_tests
is a collection of integration tests, including a suite of sample files. This is kept seperate frompmtiles
so the library remains small.
There are tests for native Dart VM, Node.js and Chrome. The integration tests require both the offical pmtiles command line, as well as http-server to be installed.
Use melos test
to run all these tests.
The specification is here https://github.com/protomaps/PMTiles/tree/main/spec/v3
BSD 2-Clause License
Copyright (c) 2023-2024, Andrew Brampton
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
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