【发布时间】：2014-08-07 03:22:02
【问题描述】：
我正在尝试将图像地图与自定义投影放在一起。我从以下 3 个 URL 中借用了代码：
https://developers.google.com/maps/documentation/javascript/examples/map-coordinates https://developers.google.com/maps/documentation/javascript/examples/maptype-image https://developers.google.com/maps/documentation/javascript/examples/map-projection-simple
我添加了代码以 10 度增量循环遍历所有 Lat 和 Lng 值，但实际上只显示了一些标记。
如果我删除该行：
mapType.projection = new MercatorProjection();
然后标记都按预期显示。这意味着我不能使用我的自定义投影，除非有更好的方法。
所有的 Javascript 代码都在下面，应该用标记向你展示月亮。
谢谢。
<!DOCTYPE html>
<html>
<head>
<title>Showing pixel and tile coordinates</title>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no">
<meta charset="utf-8">
<style>
html, body, #map-canvas {
height: 100%;
margin: 0px;
padding: 0px
}
</style>
<script src="https://maps.googleapis.com/maps/api/js?v=3.exp"></script>
<script>
var map;
var TILE_SIZE = 256;
var chicago = new google.maps.LatLng(41.850033,-87.6500523);
function modulo(n, d) {
var result = (n % d + d) % d;
return result;
}
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;
}
function degreesToRadians(deg) {
return deg * (Math.PI / 180);
}
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);
}
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;
};
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);
};
// Normalizes the coords that tiles repeat across the x axis (horizontally)
// like the standard Google map tiles.
function getNormalizedCoord(coord, zoom) {
var y = coord.y;
var x = coord.x;
// tile range in one direction range is dependent on zoom level
// 0 = 1 tile, 1 = 2 tiles, 2 = 4 tiles, 3 = 8 tiles, etc
var numTiles = 1 << zoom;
// don't repeat across y-axis (vertically)
if (y < 0 || y >= numTiles) {
return null;
}
// repeat across x-axis
if (x < 0 || x >= numTiles) {
x = modulo(x, numTiles);
}
return {
x: x,
y: y
};
}
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>');
}
function initialize() {
var mapType = new google.maps.ImageMapType({
getTileUrl: function(coord, zoom) {
var normalizedCoord = getNormalizedCoord(coord, zoom);
if (!normalizedCoord) {
return null;
}
var bound = Math.pow(2, zoom);
return 'http://mw1.google.com/mw-planetary/lunar/lunarmaps_v1/clem_bw' +
'/' + zoom + '/' + normalizedCoord.x + '/' +
(bound - normalizedCoord.y - 1) + '.jpg';
},
tileSize: new google.maps.Size(TILE_SIZE, TILE_SIZE),
maxZoom: 9,
minZoom: 0,
radius: 1738000,
name: 'MyMap'
});
mapType.projection = new MercatorProjection(); // Remove and Markers Will Show Correctly
var mapOptions = {
zoom: 3,
center: chicago
};
map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);
map.mapTypes.set('mymap', mapType);
map.setMapTypeId('mymap');
var coordInfoWindow = new google.maps.InfoWindow();
coordInfoWindow.setContent(createInfoWindowContent());
coordInfoWindow.setPosition(chicago);
coordInfoWindow.open(map);
google.maps.event.addListener(map, 'zoom_changed', function() {
coordInfoWindow.setContent(createInfoWindowContent());
coordInfoWindow.open(map);
});
for (var lat=-80; lat<85; lat+=10) {
for (var lng=-180; lng<180; lng+=10) {
var markerlatlng = new google.maps.LatLng(lat, lng);
var marker = new google.maps.Marker({
position: markerlatlng,
map: map,
title: "Moon Marker"
});
}
}
}
google.maps.event.addDomListener(window, 'load', initialize);
</script>
</head>
<body>
<div id="map-canvas"></div>
</body>
</html>
【问题讨论】：
-
请注意，fromPointToLatLng 应该采用第二个参数“noWrap”。修复有时不会使事情变得脆弱的问题，但不知道这里是否会出现这种情况。
标签： javascript google-maps-api-3 map-projections