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2022-05-31 16:21:53 -04:00
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+/* ------------------------------------------------------------------------------
+*
+*  # Showing coordinates
+*
+*  Specific JS code additions for maps_google_basic.html page
+*
+*  Version: 1.0
+*  Latest update: Aug 1, 2015
+*
+* ---------------------------------------------------------------------------- */
+
+$(function() {
+
+    // Variables
+    var map;
+    var TILE_SIZE = 256;
+    var chicago = new google.maps.LatLng(41.850033,-87.6500523);
+
+    // Minimum and maximum values
+    function bound(value, opt_min, opt_max) {
+        if (opt_min != null) value = Math.max(value, opt_min);
+        if (opt_max != null) value = Math.min(value, opt_max);
+        return value;
+    }
+
+    // Degrees to radians
+    function degreesToRadians(deg) {
+        return deg * (Math.PI / 180);
+    }
+
+    // Radians to degrees
+    function radiansToDegrees(rad) {
+        return rad / (Math.PI / 180);
+    }
+
+    // Constructor
+    function MercatorProjection() {
+        this.pixelOrigin_ = new google.maps.Point(TILE_SIZE / 2, TILE_SIZE / 2);
+        this.pixelsPerLonDegree_ = TILE_SIZE / 360;
+        this.pixelsPerLonRadian_ = TILE_SIZE / (2 * Math.PI);
+    }
+
+    // From latitude to longitude
+    MercatorProjection.prototype.fromLatLngToPoint = function(latLng, opt_point) {
+        var me = this;
+        var point = opt_point || new google.maps.Point(0, 0);
+        var origin = me.pixelOrigin_;
+
+        point.x = origin.x + latLng.lng() * me.pixelsPerLonDegree_;
+
+        // Truncating to 0.9999 effectively limits latitude to 89.189. This is
+        // about a third of a tile past the edge of the world tile.
+        var siny = bound(Math.sin(degreesToRadians(latLng.lat())), -0.9999, 0.9999);
+        point.y = origin.y + 0.5 * Math.log((1 + siny) / (1 - siny)) * -me.pixelsPerLonRadian_;
+        return point;
+    };
+
+    // From longitude to latitude
+    MercatorProjection.prototype.fromPointToLatLng = function(point) {
+        var me = this;
+        var origin = me.pixelOrigin_;
+        var lng = (point.x - origin.x) / me.pixelsPerLonDegree_;
+        var latRadians = (point.y - origin.y) / -me.pixelsPerLonRadian_;
+        var lat = radiansToDegrees(2 * Math.atan(Math.exp(latRadians)) - Math.PI / 2);
+        return new google.maps.LatLng(lat, lng);
+    };
+
+    // Create content
+    function createInfoWindowContent() {
+        var numTiles = 1 << map.getZoom();
+        var projection = new MercatorProjection();
+        var worldCoordinate = projection.fromLatLngToPoint(chicago);
+        var pixelCoordinate = new google.maps.Point(worldCoordinate.x * numTiles, worldCoordinate.y * numTiles);
+        var tileCoordinate = new google.maps.Point(
+        Math.floor(pixelCoordinate.x / TILE_SIZE),
+        Math.floor(pixelCoordinate.y / TILE_SIZE));
+
+        return [
+            'Chicago, IL',
+            'LatLng: ' + chicago.lat() + ' , ' + chicago.lng(),
+            'World Coordinate: ' + worldCoordinate.x + ' , ' + worldCoordinate.y,
+            'Pixel Coordinate: ' + Math.floor(pixelCoordinate.x) + ' , ' + Math.floor(pixelCoordinate.y),
+            'Tile Coordinate: ' + tileCoordinate.x + ' , ' + tileCoordinate.y + ' at Zoom Level: ' + map.getZoom()
+        ].join('<br>');
+    }
+
+    // Initialize
+    function initialize() {
+
+        // Options
+        var mapOptions = {
+            zoom: 10,
+            center: chicago
+        };
+
+        // Apply options
+        map = new google.maps.Map($('.map-coordinates')[0], mapOptions);
+
+        // Info window
+        var coordInfoWindow = new google.maps.InfoWindow();
+        coordInfoWindow.setContent(createInfoWindowContent());
+        coordInfoWindow.setPosition(chicago);
+        coordInfoWindow.open(map);
+
+        // Add "Change" event
+        google.maps.event.addListener(map, 'zoom_changed', function() {
+            coordInfoWindow.setContent(createInfoWindowContent());
+            coordInfoWindow.open(map);
+        });
+    }
+
+    // Load map
+    google.maps.event.addDomListener(window, 'load', initialize);
+
+});