openlayers
Version:
Build tools and sources for developing OpenLayers based mapping applications
159 lines (139 loc) • 4.06 kB
JavaScript
goog.provide('ol.proj.EPSG3857');
goog.require('ol');
goog.require('ol.math');
goog.require('ol.proj');
goog.require('ol.proj.Projection');
goog.require('ol.proj.Units');
/**
* @classdesc
* Projection object for web/spherical Mercator (EPSG:3857).
*
* @constructor
* @extends {ol.proj.Projection}
* @param {string} code Code.
* @private
*/
ol.proj.EPSG3857_ = function(code) {
ol.proj.Projection.call(this, {
code: code,
units: ol.proj.Units.METERS,
extent: ol.proj.EPSG3857.EXTENT,
global: true,
worldExtent: ol.proj.EPSG3857.WORLD_EXTENT,
getPointResolution: function(resolution, point) {
return resolution / ol.math.cosh(point[1] / ol.proj.EPSG3857.RADIUS);
}
});
};
ol.inherits(ol.proj.EPSG3857_, ol.proj.Projection);
/**
* @const
* @type {number}
*/
ol.proj.EPSG3857.RADIUS = 6378137;
/**
* @const
* @type {number}
*/
ol.proj.EPSG3857.HALF_SIZE = Math.PI * ol.proj.EPSG3857.RADIUS;
/**
* @const
* @type {ol.Extent}
*/
ol.proj.EPSG3857.EXTENT = [
-ol.proj.EPSG3857.HALF_SIZE, -ol.proj.EPSG3857.HALF_SIZE,
ol.proj.EPSG3857.HALF_SIZE, ol.proj.EPSG3857.HALF_SIZE
];
/**
* @const
* @type {ol.Extent}
*/
ol.proj.EPSG3857.WORLD_EXTENT = [-180, -85, 180, 85];
/**
* Lists several projection codes with the same meaning as EPSG:3857.
*
* @type {Array.<string>}
*/
ol.proj.EPSG3857.CODES = [
'EPSG:3857',
'EPSG:102100',
'EPSG:102113',
'EPSG:900913',
'urn:ogc:def:crs:EPSG:6.18:3:3857',
'urn:ogc:def:crs:EPSG::3857',
'http://www.opengis.net/gml/srs/epsg.xml#3857'
];
/**
* Projections equal to EPSG:3857.
*
* @const
* @type {Array.<ol.proj.Projection>}
*/
ol.proj.EPSG3857.PROJECTIONS = ol.proj.EPSG3857.CODES.map(function(code) {
return new ol.proj.EPSG3857_(code);
});
/**
* Transformation from EPSG:4326 to EPSG:3857.
*
* @param {Array.<number>} input Input array of coordinate values.
* @param {Array.<number>=} opt_output Output array of coordinate values.
* @param {number=} opt_dimension Dimension (default is `2`).
* @return {Array.<number>} Output array of coordinate values.
*/
ol.proj.EPSG3857.fromEPSG4326 = function(input, opt_output, opt_dimension) {
var length = input.length,
dimension = opt_dimension > 1 ? opt_dimension : 2,
output = opt_output;
if (output === undefined) {
if (dimension > 2) {
// preserve values beyond second dimension
output = input.slice();
} else {
output = new Array(length);
}
}
ol.DEBUG && console.assert(output.length % dimension === 0,
'modulus of output.length with dimension should be 0');
var halfSize = ol.proj.EPSG3857.HALF_SIZE;
for (var i = 0; i < length; i += dimension) {
output[i] = halfSize * input[i] / 180;
var y = ol.proj.EPSG3857.RADIUS *
Math.log(Math.tan(Math.PI * (input[i + 1] + 90) / 360));
if (y > halfSize) {
y = halfSize;
} else if (y < -halfSize) {
y = -halfSize;
}
output[i + 1] = y;
}
return output;
};
/**
* Transformation from EPSG:3857 to EPSG:4326.
*
* @param {Array.<number>} input Input array of coordinate values.
* @param {Array.<number>=} opt_output Output array of coordinate values.
* @param {number=} opt_dimension Dimension (default is `2`).
* @return {Array.<number>} Output array of coordinate values.
*/
ol.proj.EPSG3857.toEPSG4326 = function(input, opt_output, opt_dimension) {
var length = input.length,
dimension = opt_dimension > 1 ? opt_dimension : 2,
output = opt_output;
if (output === undefined) {
if (dimension > 2) {
// preserve values beyond second dimension
output = input.slice();
} else {
output = new Array(length);
}
}
ol.DEBUG && console.assert(output.length % dimension === 0,
'modulus of output.length with dimension should be 0');
for (var i = 0; i < length; i += dimension) {
output[i] = 180 * input[i] / ol.proj.EPSG3857.HALF_SIZE;
output[i + 1] = 360 * Math.atan(
Math.exp(input[i + 1] / ol.proj.EPSG3857.RADIUS)) / Math.PI - 90;
}
return output;
};