georaster-layer-for-leaflet-example/examples/ndvi.html at master · GeoTIFF/georaster-layer-for-leaflet-example · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css"/>
    <style>
      #map {
        bottom: 0;
        left: 0;
        position: absolute;
        right: 0;
        top: 0;
        z-index: 1;
      }
      #info {
        background: rgba(20, 20, 20, 0.85);
        color: lightblue;
        left: 15%;
        padding: 15px;
        position: absolute;
        top: 0;
        right: 15%;
        z-index: 2;
      }
      #info a {
        color: lightblue;
      }
    </style>
  </head>
  <body>
    <div id="info">
      You are viewing a map created with <a href="http://leafletjs.com/">LeafletJS</a> and <a href="https://github.com/geotiff/georaster-layer-for-leaflet">GeoRasterLayer for Leaflet</a>.
      <br/>
      This demo is pulling from 2 64MB Landsat 8 GeoTIFFs, but takes less than 1 MB to load through the magic of <a href="https://www.cogeo.org/">Cloud Optimized GeoTIFFs</a>.
    </div>
    <div id="map"></div>
    <script src="https://unpkg.com/chroma-js"></script>
    <script src="https://unpkg.com/leaflet@1.0.3/dist/leaflet.js"></script>
    <script src="https://unpkg.com/georaster"></script>
    <script src="https://unpkg.com/proj4"></script>
    <script src="https:///unpkg.com/georaster-layer-for-leaflet@latest"></script>
    <script>
      // initalize leaflet map
      var map = L.map('map').setView([0, 0], 5);

      // add OpenStreetMap basemap
      L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
          attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
      }).addTo(map);

      /*
        NDVI is (Near-Infrared - Red) / (Near-Infrared + Red)

        "In Landsat 8, NDVI = (Band 5 – Band 4) / (Band 5 + Band 4)." (USGS)
      */
      const baseURL = "https://landsat-pds.s3.amazonaws.com/c1/L8/024/030/LC08_L1TP_024030_20180723_20180731_01_T1/LC08_L1TP_024030_20180723_20180731_01_T1_B.TIF";
      const band4URL = baseURL.replace('B.TIF', 'B4.TIF');
      const band5URL = baseURL.replace('B.TIF', 'B5.TIF');
      const scale = chroma.scale([
        '#C7BB95',
        '#FEFEE1',
        '#6E9F62',
        '#032816',
        'black'
      ]).domain([
        0,
        .2,
        .4,
        .6,
        .8
      ]);
      Promise.all([
        parseGeoraster(band4URL),
        parseGeoraster(band5URL)
      ]).then(georasters => {
        var pixelValuesToColorFn = values => {
          const [ RED, NIR ] = values;
          const dividend = NIR - RED;
          const divisor = NIR + RED;
          let result;
          if (dividend === 0 && divisor === 0) {
            // probably no reading here
            return 'rgba(0,0,0,0)';
          }
          if (dividend === 0 || divisor === 0) {
            result = 0;
          } else {
            result = dividend === 0 ? 0 : dividend / divisor;
          }
          if (result <= 0.1) return 'blue';
          if (result >= 0.8) return 'black';
          return scale(result).hex();
        };
        var layer = new GeoRasterLayer({
          georasters,
          pixelValuesToColorFn,
          resolution: 64,
          opacity: 0.5
        });
        layer.addTo(map);
        map.fitBounds(layer.getBounds());
      });
    </script>
  </body>
</html>