Expose methods to define new proj4 definitions

src/transform.js

@@ -1,3 +1,5 @@
+var proj4 = require('proj4');
+
 //////////////////////////////////////////////////////////////////////////////
 /**
  * This purpose of this class is to provide a generic interface for computing
@@ -28,8 +30,6 @@ var transform = function (options) {
  return new transform(options);
  }
 
- var proj4 = require('proj4');
-
  var m_this = this,
  m_proj, // The raw proj4js object
  m_source, // The source projection
@@ -157,6 +157,52 @@ var transform = function (options) {
  return this;
 };
 
+/**
+ * Contains a reference to `proj4.defs`. The functions serves two
+ * purposes.
+ *
+ * 1. It is a key value mapping of all loaded projection definitions
+ * 2. It is a function that will add additional definitions.
+ *
+ * See:
+ * http://proj4js.org/
+ */
+transform.defs = proj4.defs;
+
+/**
+ * Look up a projection definition from epsg.io
+ * For the moment, we only handle `EPSG` codes.
+ *
+ * @param {string} projection A projection alias (e.g. EPSG:4326)
+ * @returns {promise} Resolves with the proj4 definition
+ */
+transform.lookup = function (projection) {
+ var $ = require('jquery');
+ var code, defer = new $.Deferred(), parts;
+
+ if (proj4.defs.hasOwnProperty(projection)) {
+ return defer.resolve(proj4.defs[projection]);
+ }
+
+ parts = projection.split(':');
+ if (parts.length !== 2 || parts[0].toUpperCase() !== 'EPSG') {
+ return defer.reject('Invalid projection code').promise();
+ }
+ code = parts[1];
+
+ return $.ajax({
+ url: 'http://epsg.io/?q=' + code + '&format=json'
+ }).then(function (data) {
+ var result = (data.results || [])[0];
+ if (!result || !result.proj4) {
+ return defer.reject(data).promise();
+ }
+
+ proj4.defs(projection, result.proj4);
+ return $.when(proj4.defs[projection]);
+ });
+};
+
 /**
  * Transform an array of coordinates from one projection into another. The
  * transformation may occur in place (modifying the input coordinate array),

tests/cases/transform.js

@@ -92,4 +92,87 @@ describe('geo.transform', function () {
  [{x: 1669792, y: -19971868}, {x: 1669792, y: -19971868}]
  ]
  );
+
+ describe('defs', function () {
+ var server;
+
+ beforeEach(function () {
+ server = sinon.fakeServer.create();
+ });
+
+ afterEach(function () {
+ server.restore();
+ });
+
+ it('predefined definitions', function () {
+ expect(geo.transform.defs.hasOwnProperty('EPSG:4326')).toBe(true);
+ expect(geo.transform.defs.hasOwnProperty('EPSG:3857')).toBe(true);
+ });
+
+ it('custom definition', function () {
+ geo.transform.defs('my projection', '+proj=longlat +datum=WGS84 +no_defs');
+ expect(geo.transform.defs.hasOwnProperty('my projection')).toBe(true);
+ var p = geo.transform({source: 'EPSG:4326', target: 'my projection'});
+
+ expect(p.forward({x: 10, y: -10, z: 0})).toEqual({x: 10, y: -10, z: 0});
+ });
+
+ it('lookup', function () {
+ var spy = sinon.spy(), request;
+ geo.transform.lookup('EPSG:5000').then(spy);
+
+ request = server.requests[0];
+ expect(request.url).toMatch(/\?q=5000/);
+ request.respond(200, {'Content-Type': 'application/json'}, JSON.stringify({
+ status: 'ok',
+ number_result: 1,
+ results: [{
+ code: '5000',
+ kind: 'CRS-PROJCRS',
+ bbox: [
+ 85.06,
+ 180.0,
+ 85.06,
+ 180.0
+ ],
+ unit: 'degree',
+ proj4: '+proj=longlat +datum=WGS84 +no_defs',
+ name: 'WGS 84',
+ area: 'World',
+ default_trans: 0,
+ trans: [],
+ accuracy: ''
+ }]
+ }));
+
+ expect(spy.calledOnce).toBe(true);
+ expect(geo.transform.defs.hasOwnProperty('EPSG:5000')).toBe(true);
+
+ geo.transform.lookup('EPSG:5000');
+ expect(server.requests.length).toBe(1);
+ });
+
+ it('invalid projection code', function () {
+ var spy = sinon.spy(), request;
+ geo.transform.lookup('EPSG:5001').fail(spy);
+
+ request = server.requests[0];
+ request.respond(200, {'Content-Type': 'application/json'}, JSON.stringify({
+ status: 'ok',
+ number_result: 0,
+ results: []
+ }));
+
+ expect(spy.calledOnce).toBe(true);
+ expect(geo.transform.defs.hasOwnProperty('EPSG:5001')).toBe(false);
+ });
+
+ it('unknown projection type', function () {
+ var spy = sinon.spy();
+ geo.transform.lookup('unknown:5002').fail(spy);
+
+ expect(spy.calledOnce).toBe(true);
+ expect(geo.transform.defs.hasOwnProperty('unknown:5002')).toBe(false);
+ });
+ });
 });