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veltman

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Base64 gif for a headless browser

Slight modification of https://bl.ocks.org/veltman/6a922b0fb6abbb815158 to save the resulting gif as a Base64 string for a headless browser to grab.

Uses blob-util for the blob-to-base64 conversion.

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

body {
    font: 24px sans-serif;
    text-align: center;
  }

div.menu {
    margin: 12px 0;
  }

body > div.half {
    display: inline-block;
    width: 400px;
    vertical-align: top;
  }

strong {
    display: block;
  }

select {
    -webkit-appearance: menulist-button;
    font-size: 24px;
  }

</style>
<style id="chart-style">

rect {
    stroke: none;
    fill: #fff;
  }

line,
  path {
    fill: none;
    stroke: #444;
    stroke-width: 1px;
  }

text {
    fill: black;
    font: 12px sans-serif;
  }

text.label {
    text-anchor: start;
  }

.country {
    font-size: 18px;
    text-anchor: middle;
  }

.year {
    font-weight: 600;
    fill: #999;
    font-size: 36px;
    text-anchor: end;
    display: none;
  }

.first .year {
    display: block;
  }

.bar {
    fill: #0eb8ba;
  }

.first .bar {
    fill: #de1e3d;
  }

</style>
<body>
  <div class="half">
    <strong>SVG</strong>
    <div class="svg"></div>
  </div>
  <div class="half">
    <strong>GIF</strong>
    <div class="gif"></div>
  </div>
<script src="//cdnjs.cloudflare.com/ajax/libs/d3/3.5.10/d3.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/queue-async/1.0.7/queue.min.js"></script>
<script src="blob-util.min.js"></script>
<script src="gif.js"></script>
<script>

var margin = {top: 10, right: 10, bottom: 36, left: 10},
    outerWidth = 400,
    outerHeight = 200,
    width = outerWidth - margin.left - margin.right,
    height = outerHeight - margin.top - margin.bottom,
    delay = 250,
    phantomReady = false;

// Standard scales and axes
var x = d3.scale.ordinal()
    .domain(d3.range(16))
    .rangeBands([0, width],0.1);

var y = d3.scale.linear()
    .range([height,0]);

var xAxis = d3.svg.axis()
    .scale(x)
    .tickSize(0)
    .tickValues(d3.range(0,17,3))
    .tickFormat(ageFormat)
    .orient("bottom");

// SVG
var outer = d3.select(".svg").append("svg")
    .attr("width",outerWidth);

// Append stylesheet
outer.append(function(){ return document.getElementById("chart-style"); });

// Explicit background color, won't inherit page background
outer.append("rect")
    .attr("class","background")
    .attr("width",outerWidth);

d3.csv("population-groups.csv", function(error, csv) {

// Make string fields numeric
  csv.forEach(function(d){
    d.year = +d.year;
    d.pct = +d.pct;
  });

// Set domain to highest pct of any group
  y.domain([0,d3.max(csv,get("pct"))]);

// Get a map/hash by country
  // key is country name, value is array of years
  var byCountry = mapByCountry(csv);

drawChart(["Japan","Nigeria"]);

function drawChart(countries) {

var data = countries.map(function(d){
      return byCountry.get(d);
    });

d3.selectAll(".background,svg").attr("height",outerHeight * data.length);

// Hide so there's not a weird flash when the frames repaint
    d3.select(".svg").style("display","none");

var numFrames = data[0].values.length;

// Append each chart within one big SVG
    var charts = outer.selectAll(".chart")
          .data(data);

var newCharts = charts.enter()
        .append("g")
          .attr("class","chart");

// Add x axes
    newCharts.append("g")
        .attr("class","axis")
        .attr("transform","translate(0 " + height + ")")
        .call(xAxis)
        .append("text")
          .attr("class","label")
          .attr("dy","2.25em")
          .text("Percentage of population by age group");

// Add year/country labels
    newCharts.append("text")
          .attr("class","country")
          .attr("dy","0.75em")
          .attr("x",width / 2);

newCharts.append("text")
        .attr("class","year")
        .attr("dy","0.75em")
        .attr("x",width);

charts.attr("transform",function(d,i){
          return "translate(" + margin.left + " " + (margin.top + outerHeight * i) + ")";
        })
        .select(".country")
          .text(get("key"));

charts.classed("first",function(d,i){
      return !i;
    });

var gif = new GIF({
      workers: 3,
      quality: 2,
      repeat: 0
    });

gif.on("progress",function(p){

d3.select(".svg").style("display","block");

// Draw frame that matches rendering progress
      drawFrame(Math.min(numFrames - 1,Math.round(p * numFrames)));

d3.select(".gif").text(d3.format("%")(p) + " rendered");

});

gif.on("finished",function(blob){

// For PhantomJS to download as Base64
      // Native FileReader doesn't work for this for some reason
      blobUtil.blobToBase64String(blob).then(function (base64String) {
        phantomReady = base64String;
      }).catch(function (err) {
        console.warn(err);
      });

d3.select(".svg").style("display","block");

d3.select(".gif")
          .text("")
          .append("img")
            .attr("src",URL.createObjectURL(blob));

var i = 0;

// Loop the SVG
      function tick(){

drawFrame(i++ % numFrames);
        setTimeout(tick,delay);

}

tick();

});

var q = queue(1);

// Queue up frames to add to gif stack
    d3.range(numFrames).forEach(function(i){
      q.defer(addFrame,i);
    });

// Once all frames are added
    q.awaitAll(function(err){

// Quit if countries changed
      if (!err) {

// Start web workers
        gif.render();

}

});

// Add a frame for a given set of data
    function addFrame(i,cb) {

drawFrame(i);

// Create a blob URL from SVG
      // including "charset=utf-8" in the blob type breaks in Safari
      var img = new Image(),
          serialized = new XMLSerializer().serializeToString(outer.node()),
          svg = new Blob([serialized], {type: "image/svg+xml"}),
          url = URL.createObjectURL(svg);

// Onload, callback to move on to next frame
      img.onload = function(){

gif.addFrame(img, {
          delay: delay,
          copy: true
        });

return cb(null);

};

img.src = url;

}

// Update the chart to frame idx
    function drawFrame(idx) {

charts.select(".year")
          .text(function(d){
            return d.values[idx].key;
          })

var bars = charts.selectAll(".bar")
          .data(function(d,i){
              return d.values[idx].values;
          });

bars.enter().append("rect")
          .attr("class","bar")
          .attr("x",function(d,i){
            return x(i);
          })
          .attr("width",x.rangeBand());

bars.attr("y",get("pct",y))
          .attr("height",function(d){
            return height - y(d.pct);
          });

}

});

// Turn big list of age group+year+country into a map by country
function mapByCountry(rows) {

// Rows are presorted
  var nested = d3.nest()
      .key(get("country"))
      .key(get("year"))
      .entries(rows);

return d3.map(nested,get("key"));

}

// Lazy equality test
function equal(a,b) {
  return a.length === b.length && a.every(function(d,i){ return d === b[i]; });
}

function ageFormat(d) {

var age = d * 5;

if (age === 75) {
      return age + "+";
    }

return age + "-" + (age + 4);

}

function get(p, f) {

if (f) {

return function(d) {
      return f(d[p]);
    };

}

if (p) {
    return function(d) {
      return d[p];
    };
  }

return function(d){
    return d;
  };

}

</script>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.10/d3.min.js

https://cdnjs.cloudflare.com/ajax/libs/queue-async/1.0.7/queue.min.js