@mapgis/geojson-vt
Version:
Slice GeoJSON data into vector tiles efficiently
69 lines (53 loc) • 2.29 kB
JavaScript
import clip from './clip.js';
import createFeature from './feature.js';
export default function wrap(features, options) {
const buffer = options.buffer / options.extent;
let merged = features;
const left = clip(features, 1, -1 - buffer, buffer, 0, -1, 2, options); // left world copy
const right = clip(features, 1, 1 - buffer, 2 + buffer, 0, -1, 2, options); // right world copy
if (left || right) {
merged = clip(features, 1, -buffer, 1 + buffer, 0, -1, 2, options) || []; // center world copy
if (left) merged = shiftFeatureCoords(left, 1).concat(merged); // merge left into center
if (right) merged = merged.concat(shiftFeatureCoords(right, -1)); // merge right into center
}
return merged;
}
function shiftFeatureCoords(features, offset) {
const newFeatures = [];
for (let i = 0; i < features.length; i++) {
const feature = features[i];
const type = feature.type;
let newGeometry;
if (type === 'Point' || type === 'MultiPoint' || type === 'LineString') {
newGeometry = shiftCoords(feature.geometry, offset);
} else if (type === 'MultiLineString' || type === 'Polygon') {
newGeometry = [];
for (const line of feature.geometry) {
newGeometry.push(shiftCoords(line, offset));
}
} else if (type === 'MultiPolygon') {
newGeometry = [];
for (const polygon of feature.geometry) {
const newPolygon = [];
for (const line of polygon) {
newPolygon.push(shiftCoords(line, offset));
}
newGeometry.push(newPolygon);
}
}
newFeatures.push(createFeature(feature.id, type, newGeometry, feature.tags));
}
return newFeatures;
}
function shiftCoords(points, offset) {
const newPoints = [];
newPoints.size = points.size;
if (points.start !== undefined) {
newPoints.start = points.start;
newPoints.end = points.end;
}
for (let i = 0; i < points.length; i += 3) {
newPoints.push(points[i] + offset, points[i + 1], points[i + 2]);
}
return newPoints;
}