Satellite Raster

Static tiled raster version of Mike Bostock’s satellite projection example

Minimal Mercator tiles from a [MapBox terrain example](http://a.tiles.mapbox.com/v3/examples.map-4l7djmvo/page.html) are [automatic computed](http://www.jasondavies.com/maps/tile/) and reprojected on-the-fly. Unfortunately, distortion is too great to support zooming at the moment.

<!DOCTYPE html>
<meta charset="utf-8">
<title>Satellite Raster</title>
<style>
@import url(../../maps.css);

#map {
  position: relative;
  margin: 0 auto;
  overflow: hidden;
  clip-path: url(#clip);
}

canvas {
  cursor: auto;
}

.layer0 {
  -webkit-transform: scale(.5);
  -webkit-transform-origin: 0 0 0;
}

.layer {
  -webkit-transform-origin: 0 0 0;
}

.tile {
  position: absolute;
}
</style>

var ratio = 2,
    radians = Math.PI / 180,
    width = 960 * ratio,
    height = 960 * ratio,
    p = .5;

var projection = d3.geo.satellite()
    .translate([width / 2, .65 * height / 2])
    .scale(5500 * ratio)
    .distance(1.1)
    .rotate([76.00, -34.50, 32.12])
    .center([-2, 5])
    .tilt(25)
    .clipAngle(Math.acos(1 / 1.1) * 180 / Math.PI - 1e-6)
    .clipExtent([[p, p], [width - p, height - p]]);

var path = d3.geo.path().projection(projection);

var layer = d3.select("#map")
    .style("width", width / ratio + "px")
    .style("height", height / ratio + "px")
  .append("div").attr("class", "layer0")
  .append("div").attr("class", "layer")

var imgCanvas = document.createElement("canvas"),
    imgContext = imgCanvas.getContext("2d");
 
function onload(d, canvas, pot) {
  var t = projection.translate(),
      s = projection.scale(),
      c = projection.clipExtent(),
      cr = Math.cos(projection.clipAngle() * radians),
      image = d.image,
      dx = image.width,
      dy = image.height,
      k = d.key,
      width = 1 << k[2];

projection.translate([0, 0]).scale(1 << pot).clipExtent(null);

imgCanvas.width = dx, imgCanvas.height = dy;
  imgContext.drawImage(image, 0, 0, dx, dy);

var bounds = path.bounds(d),
      x0 = d.x0 = bounds[0][0] | 0,
      y0 = d.y0 = bounds[0][1] | 0,
      x1 = bounds[1][0] + 1 | 0,
      y1 = bounds[1][1] + 1 | 0;

var λ0 = k[0] / width * 360 - 180,
      λ1 = (k[0] + 1) / width * 360 - 180,
      φ1 = mercatorφ(k[1] / width * 360 - 180),
      φ0 = mercatorφ((k[1] + 1) / width * 360 - 180);

var width = canvas.width = x1 - x0,
      height = canvas.height = y1 - y0,
      context = canvas.getContext("2d");

if (width > 0 && height > 0) {
    var sourceData = imgContext.getImageData(0, 0, dx, dy).data,
        target = context.createImageData(width, height),
        targetData = target.data;
   
    for (var y = y0, i = -1; y < y1; ++y) {
      for (var x = x0; x < x1; ++x) {
        var p = projection.invert([x, y]), λ = p[0], φ = p[1];
        if (isNaN(λ) || isNaN(φ) || λ > λ1 || λ < λ0 || φ > φ1 || φ < φ0) { i += 4; continue; }

var q = (((λ - λ0) / (λ1 - λ0) * dx | 0) + ((φ1 - φ) / (φ1 - φ0) * dy | 0) * dx) * 4;
        //var q = ((90 - φ) / 180 * dy | 0) * dx + ((180 + λ) / 360 * dx | 0) << 2;
        targetData[++i] = sourceData[q];
        targetData[++i] = sourceData[++q];
        targetData[++i] = sourceData[++q];
        targetData[++i] = 255;
      }
    }
    context.putImageData(target, 0, 0);
  }
 
  d3.selectAll([canvas])
      .style("left", x0 + "px")
      .style("top", y0 + "px");

projection.translate(t).scale(s).clipExtent(c);
}

redraw();

function redraw() {
  // TODO improve zoom level computation
  var pot = Math.log(projection.scale()) / Math.LN2 | 0,
      ds = projection.scale() / (1 << pot),
      t = projection.translate(),
      z = pot - 6;

layer.style("-webkit-transform", "translate(" + t.map(pixel) + ")scale(" + ds + ")");

function key(d) { return d.key.join(", "); }

function mercatorφ(y) {
  return Math.atan(Math.exp(-y * Math.PI / 180)) * 360 / Math.PI - 90;
}

function pixel(d) { return (d | 0) + "px"; }

</script>

Modified http://www.jasondavies.com/d3.min.js to a secure url

Modified http://www.jasondavies.com/maps/d3.geo.projection.min.js to a secure url

Modified http://www.jasondavies.com/maps/topojson.min.js to a secure url

Modified http://www.jasondavies.com/maps/d3.quadtiles.js to a secure url

https://www.jasondavies.com/d3.min.js

https://www.jasondavies.com/maps/d3.geo.projection.min.js

https://www.jasondavies.com/maps/topojson.min.js

https://www.jasondavies.com/maps/d3.quadtiles.js