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node_modules/proj4/lib/projections/moll.js

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+import adjust_lon from '../common/adjust_lon';
+export function init() {}
+import {EPSLN} from '../constants/values';
+/* Mollweide forward equations--mapping lat,long to x,y
+    ----------------------------------------------------*/
+export function forward(p) {
+
+  /* Forward equations
+      -----------------*/
+  var lon = p.x;
+  var lat = p.y;
+
+  var delta_lon = adjust_lon(lon - this.long0);
+  var theta = lat;
+  var con = Math.PI * Math.sin(lat);
+
+  /* Iterate using the Newton-Raphson method to find theta
+      -----------------------------------------------------*/
+  while (true) {
+    var delta_theta = -(theta + Math.sin(theta) - con) / (1 + Math.cos(theta));
+    theta += delta_theta;
+    if (Math.abs(delta_theta) < EPSLN) {
+      break;
+    }
+  }
+  theta /= 2;
+
+  /* If the latitude is 90 deg, force the x coordinate to be "0 + false easting"
+       this is done here because of precision problems with "cos(theta)"
+       --------------------------------------------------------------------------*/
+  if (Math.PI / 2 - Math.abs(lat) < EPSLN) {
+    delta_lon = 0;
+  }
+  var x = 0.900316316158 * this.a * delta_lon * Math.cos(theta) + this.x0;
+  var y = 1.4142135623731 * this.a * Math.sin(theta) + this.y0;
+
+  p.x = x;
+  p.y = y;
+  return p;
+}
+
+export function inverse(p) {
+  var theta;
+  var arg;
+
+  /* Inverse equations
+      -----------------*/
+  p.x -= this.x0;
+  p.y -= this.y0;
+  arg = p.y / (1.4142135623731 * this.a);
+
+  /* Because of division by zero problems, 'arg' can not be 1.  Therefore
+       a number very close to one is used instead.
+       -------------------------------------------------------------------*/
+  if (Math.abs(arg) > 0.999999999999) {
+    arg = 0.999999999999;
+  }
+  theta = Math.asin(arg);
+  var lon = adjust_lon(this.long0 + (p.x / (0.900316316158 * this.a * Math.cos(theta))));
+  if (lon < (-Math.PI)) {
+    lon = -Math.PI;
+  }
+  if (lon > Math.PI) {
+    lon = Math.PI;
+  }
+  arg = (2 * theta + Math.sin(2 * theta)) / Math.PI;
+  if (Math.abs(arg) > 1) {
+    arg = 1;
+  }
+  var lat = Math.asin(arg);
+
+  p.x = lon;
+  p.y = lat;
+  return p;
+}
+
+export var names = ["Mollweide", "moll"];
+export default {
+  init: init,
+  forward: forward,
+  inverse: inverse,
+  names: names
+};