Paint by Numbers by mbostock

index.html

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

path {
  stroke-linejoin: round;
  stroke-linecap: round;
}

.background {
  fill: none;
  stroke: #ddd;
}

.foreground {
  fill: none;
  pointer-events: all;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 600;

var projection = d3.geo.albersUsa()
    .scale(1280)
    .translate([width / 2, height / 2]);

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

var color = d3.scale.category10().domain(d3.range(9)),
    selectedColor = 0,
    dragColor;

var components = color.domain().map(function() { return []; });

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

var legend = svg.append("g")
    .attr("class", "legend")
    .attr("transform", "translate(" + ((width - color.domain().length * 24) / 2) + ",10)")
    .style("cursor", "pointer")
  .selectAll("rect")
    .data(color.domain())
  .enter().append("rect")
    .attr("x", function(d) { return d * 24; })
    .attr("width", 24 - 3)
    .attr("height", 24 - 3)
    .style("stroke", function(d) { return d ? null : "#000"; })
    .style("fill", color)
    .on("click", clicklegend);

d3.select(self)
    .on("keydown", keydown)
    .node().focus();

d3.json("/mbostock/raw/4090846/us.json", function(error, us) {
  if (error) throw error;

  var bisectId = d3.bisector(function(d) { return d.id; }).left;

  var features = topojson.feature(us, us.objects.states).features;

  svg.append("path")
      .datum(topojson.mesh(us, us.objects.states))
      .attr("class", "background")
      .attr("d", path);

  var merge = svg.append("g")
      .attr("class", "merge")
    .selectAll("path")
      .data(components)
    .enter().append("path")
      .style("fill", function(d, i) { return color(i); })
      .style("stroke", function(d, i) { return d3.lab(color(i)).darker(); });

  svg.append("g")
      .attr("class", "foreground")
      .style("cursor", "pointer")
      .style("stroke-opacity", .5)
    .selectAll("path")
      .data(features)
    .enter().append("path")
      .attr("d", function(d) { d.color = null; return path(d); })
      .on("mouseover", function() { this.style.stroke = "black"; })
      .on("mouseout", function() { this.style.stroke = "none"; })
      .call(d3.behavior.drag()
        .on("dragstart", dragstart)
        .on("drag", drag));

  top.location.hash.split("").slice(1, features.length).forEach(function(c, i) {
    if ((c = +c) >= 0 && c < 10) assign(features[i], c ? c - 1 : null);
  });

  redraw();

  function dragstart() {
    var feature = d3.event.sourceEvent.target.__data__;
    if (assign(feature, dragColor = feature.color === selectedColor ? null : selectedColor)) redraw();
  }

  function drag() {
    var feature = d3.event.sourceEvent.target.__data__;
    if (feature && assign(feature, dragColor)) redraw();
  }

  function assign(feature, color) {
    if (feature.color === color) return false;
    if (feature.color !== null) {
      var component = components[feature.color];
      component.splice(bisectId(component, feature.id), 1);
      feature.color = null;
    }
    if (color !== null) {
      var component = components[color];
      component.splice(bisectId(component, feature.id), 0, feature);
      feature.color = color;
    }
    return true;
  }

  function redraw() {
    merge.data(components).attr("d", function(d) { return path({type: "FeatureCollection", features: d}) || "M0,0"; });
    top.history.replaceState(null, null, "#" + features.map(function(d) { return d.color === null ? "0" : d.color + 1; }).join(""));
  }
});

function clicklegend(d) {
  legend[0][selectedColor].style.stroke = null;
  legend[0][selectedColor = d].style.stroke = "#000";
}

function keydown() {
  if (d3.event.keyCode >= 48 && d3.event.keyCode < 58) {
    var i = d3.event.keyCode - 49;
    if (i < 0) i = 10;
    clicklegend(i);
  }
}

d3.select(self.frameElement).style("height", height + "px");

</script>