block by mbostock 4329423

Raster Reprojection

Full Screen

The NASA Blue Marble is reprojected using d3.geo.kavrayskiy7’s invert function. Jason Davies has since done some amazing work on reprojecting raster tiles.

Updated Example →

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  background: #222;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/d3.geo.projection.v0.min.js"></script>
<script>

var width = 960,
    height = 500;

var projection = d3.geo.kavrayskiy7();

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

var canvas = d3.select("body").append("canvas")
    .attr("width", width)
    .attr("height", height);

var context = canvas.node().getContext("2d");

var image = new Image;
image.onload = onload;
image.src = "readme-blue-marble.jpg";

function onload() {
  var dx = image.width,
      dy = image.height;

  context.drawImage(image, 0, 0, dx, dy);

  var sourceData = context.getImageData(0, 0, dx, dy).data,
      target = context.createImageData(width, height),
      targetData = target.data;

  for (var y = 0, i = -1; y < height; ++y) {
    for (var x = 0; x < width; ++x) {
      var p = projection.invert([x, y]), λ = p[0], φ = p[1];
      if (λ > 180 || λ < -180 || φ > 90 || φ < -90) { i += 4; continue; }
      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.clearRect(0, 0, width, height);
  context.putImageData(target, 0, 0);
}

</script>