var overlay;
USCitiesOverlay.prototype = new google.maps.OverlayView();
function USCitiesOverlay(map) {
this._map = map;
this._cities = [];
this._radius = 6;
this._container = document.createElement("div");
this._container.id = "citieslayer";
this.setMap(map);
this.addCity = function (lat, lng,population) {
this._cities.push({position: new google.maps.LatLng(lat,lng),population: population});
};
}
USCitiesOverlay.prototype.createCityIcon = function (id,pos,population) {
var cityIcon = document.createElement('canvas');
cityIcon.id = 'cityicon_' + id;
this._radius = population / 100000;
cityIcon.width = cityIcon.height = this._radius * 2;
cityIcon.style.width = cityIcon.width + 'px';
cityIcon.style.height = cityIcon.height + 'px';
cityIcon.style.left = (pos.x - this._radius) + 'px';
cityIcon.style.top = (pos.y - this._radius) + 'px';
cityIcon.style.position = "absolute";
var centerX = cityIcon.width / 2;
var centerY = cityIcon.height / 2;
var ctx = cityIcon.getContext('2d');
ctx.fillStyle = 'rgba(160,16,0,0.6)';
ctx.beginPath();
ctx.arc(centerX, centerY, this._radius, 0, Math.PI * 2, true);
ctx.fill();
return cityIcon;
};
USCitiesOverlay.prototype.ensureCityIcon = function (id,pos,population) {
var cityIcon = document.getElementById("cityicon_" + id);
if(cityIcon){
cityIcon.style.left = (pos.x - this._radius) + 'px';
cityIcon.style.top = (pos.y - this._radius) + 'px';
return cityIcon;
}
return this.createCityIcon(id,pos,population);
};
USCitiesOverlay.prototype.onAdd = function () {
var panes = this.getPanes();
panes.overlayLayer.appendChild(this._container);
};
USCitiesOverlay.prototype.draw = function () {
var zoom = this._map.getZoom();
var overlayProjection = this.getProjection();
var container = this._container;
this._cities.forEach(function(city,idx){
var xy = overlayProjection.fromLatLngToDivPixel(city.position);
var cityIcon = overlay.ensureCityIcon(idx,xy,city.population);
container.appendChild(cityIcon);
});
};
USCitiesOverlay.prototype.onRemove = function () {
this._container.parentNode.removeChild(this._container);
this._container = null;
};
function getRandomInterval(min, max) {
return Math.random() * (max - min) + min;
}
function generateCityMap(count) {
var citymap = [];
var minPos = new google.maps.LatLng(49.25, -123.1);
var maxPos = new google.maps.LatLng(34.052234, -74.005973);
for(var i = 0; i < count;i++)
{
var lat = getRandomInterval(minPos.lat(),maxPos.lat());
var lng = getRandomInterval(minPos.lng(),maxPos.lng());
var population = getRandomInterval(100000,1000000);
citymap.push({
location: new google.maps.LatLng(lat, lng),
population: population
});
}
return citymap;
}
function initialize() {
var mapOptions = {
zoom: 4,
center: new google.maps.LatLng(37.09024, -95.712891),
mapTypeId: google.maps.MapTypeId.TERRAIN
};
var map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);
overlay = new USCitiesOverlay(map);
var citymap = generateCityMap(1000);
citymap.forEach(function(city){
overlay.addCity(city.location.lat(), city.location.lng(),city.population);
});
}
google.maps.event.addDomListener(window, 'load', initialize);
html, body, #map-canvas {
height: 100%;
margin: 0px;
padding: 0px;
}
<script src="https://maps.googleapis.com/maps/api/js?v=3.exp&signed_in=true"></script>
<div id="map-canvas"></div>