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Gif rendering - SVG to GIF

Testing in-browser gif generation from an SVG with gif.js. Works in recent Chrome/Safari/Firefox.

Process:

Create a standard SVG line chart.
Step through in-between frames of the line chart: for each one, update the SVG, render to an image, add the image element to a stack of gif frames.
Render frames together in the background using gif.js web workers.
When rendering's complete, add the blob URL as an image and start the SVG on an infinite loop with d3.timer (gratuitous).

See also: Gif Globe, Gif New Jersey

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

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

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

strong {
    display: block;
  }

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

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

line,
  path {
    fill: none;
  }

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

line {
    stroke-width: 0.5px;
    stroke: #e0e0e0;
  }

.axis path {
    display: none;
  }

path.price {
    stroke: #e51133;
    fill: none;
  }

</style>
<body>
  <div>
    <strong>SVG</strong>
    <div class="svg"></div>
  </div>
  <div>
    <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="gif.js"></script>
<script>

var margin = {top: 20, right: 5, bottom: 30, left: 60},
    outerWidth = 400,
    outerHeight = 320,
    width = outerWidth - margin.left - margin.right,
    height = outerHeight - margin.top - margin.bottom,
    frames = 40,
    duration = 2000;

// Standard scales and axes
var x = d3.time.scale()
    .range([0, width]);

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

var xAxis = d3.svg.axis()
    .scale(x)
    .tickSize(-height)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .tickSize(-width)
    .orient("left");

var line = d3.svg.line()
    .x(function(d){ return x(d.date); })
    .y(function(d){ return y(d.close); });

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

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

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

// Margin convention
var svg = outer.append("g")
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.csv("sp-500.csv", function(error, data) {
  if (error) throw error;

data.forEach(function(d){
    d.date = new Date(d.date);
    d.close = +d.close;
  });

x.domain(d3.extent(data,function(d){ return d.date; }));
  y.domain(d3.extent(data,function(d){ return d.close; }));

svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

svg.append("g")
      .attr("class", "y axis")
      .call(yAxis);

var path = svg.append("path")
      .attr("class","price")
      .attr("d",line(data));

var totalLength = path.node().getTotalLength();

var gif = new GIF({
    workers: 3,
    quality: 1,
    repeat: 0
  });

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

drawFrame(p * duration);

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

});

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

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

d3.timer(drawFrame);

});

// Sequential queue to ensure frames are added in order
  // Probably not necessary but onload behavior is a little unpredictable
  var q = queue(1);

// Queue up frames to add to gif stack
  d3.range(frames).forEach(function(f){
    q.defer(addFrame,f * duration / (frames - 1));
  });

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

// Show SVG as progress bar
    outer.style("display","block");

// Start web workers
    gif.render();

});

// Add a frame for time t
  function addFrame(t,cb) {

// Update SVG
    drawFrame(t);

// 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: duration / frames,
        copy: true
      });

cb(null,t);

};

img.src = url;

}

function drawFrame(t) {

// Need to catch 0% and 100%
    // Surely a smarter way to do this
    if (t > duration) {
      t = t % duration;
    }

var length = totalLength * t / duration;

path.attr("stroke-dasharray",length + " " + totalLength);

}

});

</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