node-red-contrib-tak-registration/node_modules/topojson-server/src/prequantize.js

A Node-RED node to register to TAK and to help wrap files as datapackages to send to TAK

import {hasOwnProperty} from "./object.js";

export default function(objects, bbox, n) {
  var x0 = bbox[0],
      y0 = bbox[1],
      x1 = bbox[2],
      y1 = bbox[3],
      kx = x1 - x0 ? (n - 1) / (x1 - x0) : 1,
      ky = y1 - y0 ? (n - 1) / (y1 - y0) : 1;

  function quantizePoint(input) {
    return [Math.round((input[0] - x0) * kx), Math.round((input[1] - y0) * ky)];
  }

  function quantizePoints(input, m) {
    var i = -1,
        j = 0,
        n = input.length,
        output = new Array(n), // pessimistic
        pi,
        px,
        py,
        x,
        y;

    while (++i < n) {
      pi = input[i];
      x = Math.round((pi[0] - x0) * kx);
      y = Math.round((pi[1] - y0) * ky);
      if (x !== px || y !== py) output[j++] = [px = x, py = y]; // non-coincident points
    }

    output.length = j;
    while (j < m) j = output.push([output[0][0], output[0][1]]);
    return output;
  }

  function quantizeLine(input) {
    return quantizePoints(input, 2);
  }

  function quantizeRing(input) {
    return quantizePoints(input, 4);
  }

  function quantizePolygon(input) {
    return input.map(quantizeRing);
  }

  function quantizeGeometry(o) {
    if (o != null && hasOwnProperty.call(quantizeGeometryType, o.type)) quantizeGeometryType[o.type](o);
  }

  var quantizeGeometryType = {
    GeometryCollection: function(o) { o.geometries.forEach(quantizeGeometry); },
    Point: function(o) { o.coordinates = quantizePoint(o.coordinates); },
    MultiPoint: function(o) { o.coordinates = o.coordinates.map(quantizePoint); },
    LineString: function(o) { o.arcs = quantizeLine(o.arcs); },
    MultiLineString: function(o) { o.arcs = o.arcs.map(quantizeLine); },
    Polygon: function(o) { o.arcs = quantizePolygon(o.arcs); },
    MultiPolygon: function(o) { o.arcs = o.arcs.map(quantizePolygon); }
  };

  for (var key in objects) {
    quantizeGeometry(objects[key]);
  }

  return {
    scale: [1 / kx, 1 / ky],
    translate: [x0, y0]
  };
}