proj4/lib/common/nad_intr.js

Proj4js is a JavaScript library to transform point coordinates from one coordinate system to another, including datum transformations.

var nadInterBreakout = require("./nadInterBreakout");

module.exports = function(pin, ct) {
  // force computation by decreasing by 1e-7 to be as closed as possible
  // from computation under C:C++ by leveraging rounding problems ...
  var t = {
    x: (pin.x - 1e-7) / ct.del[0],
    y: (pin.y - 1e-7) / ct.del[1]
  };
  var indx = {
    x: Math.floor(t.x),
    y: Math.floor(t.y)
  };
  var frct = {
    x: t.x - 1 * indx.x,
    y: t.y - 1 * indx.y
  };
  var val = {
    x: Number.NaN,
    y: Number.NaN
  };


  var temp = nadInterBreakout(indx, frct, 'x', 0, ct);
  if (temp) {
    indx = temp[0];
    frct = temp[1];
  }
  else {
    return val;
  }
  temp = nadInterBreakout(indx, frct, 'y', 1, ct);
  if (temp) {
    indx = temp[0];
    frct = temp[1];
  }
  else {
    return val;
  }
  var inx = (indx.y * ct.lim[0]) + indx.x;
  var f00 = {
    x: ct.cvs[inx][0],
    y: ct.cvs[inx][1]
  };
  inx++;
  var f10 = {
    x: ct.cvs[inx][0],
    y: ct.cvs[inx][1]
  };
  inx += ct.lim[0];
  var f11 = {
    x: ct.cvs[inx][0],
    y: ct.cvs[inx][1]
  };
  inx--;
  var f01 = {
    x: ct.cvs[inx][0],
    y: ct.cvs[inx][1]
  };
  var m11 = frct.x * frct.y,
    m10 = frct.x * (1 - frct.y),
    m00 = (1 - frct.x) * (1 - frct.y),
    m01 = (1 - frct.x) * frct.y;
  val.x = (m00 * f00.x + m10 * f10.x + m01 * f01.x + m11 * f11.x);
  val.y = (m00 * f00.y + m10 * f10.y + m01 * f01.y + m11 * f11.y);
  return val;
};