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Use true, not naïve, centroid

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Chandler Swift 2025-01-03 23:42:46 -06:00
parent 2842dd75ab
commit f7f662bed1
Signed by: chandlerswift
GPG key ID: A851D929D52FB93F
1 changed files with 25 additions and 8 deletions
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map.html
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@ -28,7 +28,7 @@
.label div {
position: relative;
left: -50%;
top: 10px;
top: -50%;
text-shadow: 0 0 2px white;
}
.leaflet-popup-content-wrapper {
@ -139,6 +139,28 @@
</div>`;
document.getElementById('lightbox').style.display = 'block';
}
function calculateCentroid(points) {
// https://en.wikipedia.org/wiki/Centroid#Of_a_polygon
let area = 0;
let centroidLat = 0;
let centroidLng = 0;
for (let i = 0; i < points.length; i++) {
const { lat: lat1, lng: lng1 } = points[i];
const { lat: lat2, lng: lng2 } = points[(i + 1) % points.length]; // Next vertex, wrapping around
const determinant = lat1 * lng2 - lng1 * lat2;
area += determinant;
centroidLat += (lat1 + lat2) * determinant;
centroidLng += (lng1 + lng2) * determinant;
}
area *= 0.5;
centroidLat /= (6 * area);
centroidLng /= (6 * area);
return [centroidLat, centroidLng];
}
(async function() {
const map = L.map('map', {
minZoom: 15,
@ -177,13 +199,8 @@
L.geoJSON(plats, {
filter: feature => !feature.properties.TAO_NAME.toLowerCase().includes("lawrence deer club"),
onEachFeature: function(feature, layer) {
const latLngs = layer.getLatLngs()[0];
const centerish = [ // TODO: actual centroid
latLngs.reduce((acc, i) => acc + i.lat, 0) / latLngs.length,
latLngs.reduce((acc, i) => acc + i.lng, 0) / latLngs.length,
];
const label = L.marker(centerish, {
const centroid = calculateCentroid(layer.getLatLngs()[0]);
const label = L.marker(centroid, {
icon: L.divIcon({
iconSize: null,
className: "label",