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index.js
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index.js
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// [START maps_map_projection_simple]
// This example defines an image map type using the Gall-Peters
// projection.
// https://en.wikipedia.org/wiki/Gall%E2%80%93Peters_projection
function initMap() {
// Create a map. Use the Gall-Peters map type.
const map = new google.maps.Map(document.getElementById("map"), {
zoom: 0,
center: { lat: 0, lng: 0 },
mapTypeControl: false,
});
initGallPeters();
map.mapTypes.set("gallPeters", gallPetersMapType);
map.setMapTypeId("gallPeters");
// Show the lat and lng under the mouse cursor.
const coordsDiv = document.getElementById("coords");
map.controls[google.maps.ControlPosition.TOP_CENTER].push(coordsDiv);
map.addListener("mousemove", (event) => {
coordsDiv.textContent =
"lat: " +
Math.round(event.latLng.lat()) +
", " +
"lng: " +
Math.round(event.latLng.lng());
});
// Add some markers to the map.
map.data.setStyle((feature) => {
return {
title: feature.getProperty("name"),
optimized: false,
};
});
map.data.addGeoJson(cities);
}
let gallPetersMapType;
function initGallPeters() {
const GALL_PETERS_RANGE_X = 800;
const GALL_PETERS_RANGE_Y = 512;
// Fetch Gall-Peters tiles stored locally on our server.
gallPetersMapType = new google.maps.ImageMapType({
getTileUrl: function (coord, zoom) {
const scale = 1 << zoom;
// Wrap tiles horizontally.
const x = ((coord.x % scale) + scale) % scale;
// Don't wrap tiles vertically.
const y = coord.y;
if (y < 0 || y >= scale) return "";
return (
"https://developers.google.com/maps/documentation/" +
"javascript/examples/full/images/gall-peters_" +
zoom +
"_" +
x +
"_" +
y +
".png"
);
},
tileSize: new google.maps.Size(GALL_PETERS_RANGE_X, GALL_PETERS_RANGE_Y),
minZoom: 0,
maxZoom: 1,
name: "Gall-Peters",
});
// Describe the Gall-Peters projection used by these tiles.
gallPetersMapType.projection = {
fromLatLngToPoint: function (latLng) {
const latRadians = (latLng.lat() * Math.PI) / 180;
return new google.maps.Point(
GALL_PETERS_RANGE_X * (0.5 + latLng.lng() / 360),
GALL_PETERS_RANGE_Y * (0.5 - 0.5 * Math.sin(latRadians))
);
},
fromPointToLatLng: function (point, noWrap) {
const x = point.x / GALL_PETERS_RANGE_X;
const y = Math.max(0, Math.min(1, point.y / GALL_PETERS_RANGE_Y));
return new google.maps.LatLng(
(Math.asin(1 - 2 * y) * 180) / Math.PI,
-180 + 360 * x,
noWrap
);
},
};
}
// GeoJSON, describing the locations and names of some cities.
const cities = {
type: "FeatureCollection",
features: [
{
type: "Feature",
geometry: { type: "Point", coordinates: [-87.65, 41.85] },
properties: { name: "Chicago" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [-149.9, 61.218] },
properties: { name: "Anchorage" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [-99.127, 19.427] },
properties: { name: "Mexico City" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [-0.126, 51.5] },
properties: { name: "London" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [28.045, -26.201] },
properties: { name: "Johannesburg" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [15.322, -4.325] },
properties: { name: "Kinshasa" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [151.207, -33.867] },
properties: { name: "Sydney" },
},
{
type: "Feature",
geometry: { type: "Point", coordinates: [0, 0] },
properties: { name: "0°N 0°E" },
},
],
};
// [END maps_map_projection_simple]