sample-to-geojson

#!/usr/bin/env node

var through = require('through2')
var tilebelt = require('tilebelt')
var readSample = require('./lib/read-sample')
var geojsonStream = require('geojson-stream')
var argv = require('minimist')(process.argv.slice(2))

readSample(argv)
.pipe(through.obj(function (tile, _, next) {
  var bbox = tilebelt.tileToBBOX([tile[1], tile[2], tile[0]])

  // quantize based on zoom level
  var z = tile[0]
  var pixel = 360 / 256 / Math.pow(2, z)
  var places = Math.max(0, -Math.floor(Math.log10(pixel)))
  bbox = bbox.map(function (c) {
    return parseFloat(c.toFixed(places))
  })

  if (argv.polygons) {
    var poly = {
      type: 'Polygon',
      coordinates: [[
        [bbox[0], bbox[1]],
        [bbox[0], bbox[3]],
        [bbox[2], bbox[3]],
        [bbox[2], bbox[1]],
        [bbox[0], bbox[1]]
      ]]
    }
    this.push(feature(tile, poly))
  }
  var point = {
    type: 'Point',
    coordinates: [
      (bbox[0] + bbox[2]) / 2,
      (bbox[1] + bbox[3]) / 2
    ]
  }
  this.push(feature(tile, point))
  next()
}))
.pipe(geojsonStream.stringify())
.pipe(process.stdout)

function feature (tile, geometry) {
  return {
    type: 'Feature',
    properties: {
      tile: tile.join('/'),
      x: tile[1],
      y: tile[2],
      z: tile[0]
    },
    geometry: geometry
  }
}