@loaders.gl/mvt
Version:
Loader for Mapbox Vector Tiles
42 lines (41 loc) • 1.53 kB
JavaScript
// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
// Forked from https://github.com/mapbox/geojson-vt under compatible ISC license
/**
* Transforms the coordinates of each protoFeature in the given protoTile from
* mercator-projected space into (extent x extent) protoTile space.
*/
export function transformTile(protoTile, extent) {
if (protoTile.transformed) {
return protoTile;
}
const z2 = 1 << protoTile.z;
const tx = protoTile.x;
const ty = protoTile.y;
for (const protoFeature of protoTile.protoFeatures) {
const geom = protoFeature.geometry;
const simplifiedType = protoFeature.simplifiedType;
protoFeature.geometry = [];
if (simplifiedType === 1) {
for (let j = 0; j < geom.length; j += 2) {
protoFeature.geometry.push(transformPoint(geom[j], geom[j + 1], extent, z2, tx, ty));
}
}
else {
for (let j = 0; j < geom.length; j++) {
const ring = [];
for (let k = 0; k < geom[j].length; k += 2) {
ring.push(transformPoint(geom[j][k], geom[j][k + 1], extent, z2, tx, ty));
}
protoFeature.geometry.push(ring);
}
}
}
protoTile.transformed = true;
return protoTile;
}
// eslint-disable-next-line max-params
function transformPoint(x, y, extent, z2, tx, ty) {
return [Math.round(extent * (x * z2 - tx)), Math.round(extent * (y * z2 - ty))];
}