d3experiments/cdf.html at master · jinroh/d3experiments · GitHub

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<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<script src="d3.js"></script>
<style>
body {
  font: 10px sans-serif;
}
#main {
  position: relative;
  width: 50%;
  margin: auto;
}
canvas {
  padding: 0;
  margin: 0;
}
svg {
  position: absolute;
  top: 0;
  bottom: 0;
}
.histo {
  fill-opacity: .4;
  stroke-width: 2;
}
</style>
<title></title>
</head>
<body>
<div id="main"></div>
<script>
'use strict';
function load() {
  var image  = this,
      width  = image.width,
      height = image.height,
      data   = d3.range(3).map(function() { return [] }),

      rgb = d3.scale.ordinal().domain(d3.range(3)).range(["red", "green", "blue"]),
      x = d3.scale.linear().domain([0, 255]).range([0, width]),
      y = d3.scale.linear().range([0, height / 4]),

      histos = ["red", "green", "blue"];

  var svg, histo, pixels, canvas;

  var empty = Array(256);
  for (var i = 0; i < 256; i++) { empty[i] = 0; }

  function histogram(p, i) {
    var d = empty.slice();
    for (; i < p.data.length; i += 4) {
      d[p.data[i]]++;
    }
    return d;
  }

  function normalize(p, i) {
    var H = histogram(p, i),
        c = cdf(H, p.data.length / 4);
    for (; i < p.data.length; i += 4) {
      p.data[i] = (H.length - 1) * c[p.data[i]];
    }
    return p;
  }

  function cdf(histo, size) {
    var cdf = [histo[0] / size];
    for (var i = 1; i < histo.length; i++) {
      cdf[i] = histo[i] / size + cdf[i - 1];
    }
    return cdf;
  }

  var area = d3.svg.area()
    .x(function(d, i) { return x(i); })
    .y0(height)
    .y1(function(d) { return height - y(d); })
    .interpolate("basis");

  svg = d3.select("#main")
    .append("svg")
      .attr("width", width)
      .attr("height", height)
    .append("g")

  d3.select("#main")
    .append("canvas")
    .attr("width", width)
    .attr("height", height)
    .each(function() {
      var context = this.getContext('2d');
      context.drawImage(image, 0, 0);
      pixels = function() {
        return context.getImageData(0, 0, width, height);
      }
      canvas = function(pixels) {
        context.putImageData(pixels, 0, 0);
      }
    });

  d3.select("#main").selectAll("input")
    .data(histos).enter().append("input")
    .attr("type", "checkbox")
    .each(function(d, i) {
      data[i] = histogram(pixels(), i);
    })
    .on("change", function(d, i) {
      var h, n;
      if (this.checked) {
        n = normalize(pixels(), i);
        h = histogram(n, i);
        canvas(n);
      } else {
        h = histogram(pixels(), i);
      }
      data[i] = h;
      redraw();
    })

  function draw() {
    var max = Math.max(d3.max(data[0]), d3.max(data[1]), d3.max(data[2]));
    y.domain([0, max]);
    histo = svg.selectAll(".histo")
      .data(data).enter().append("path")
      .attr("class", "histo")
      .attr("fill", function(d, i) { return rgb(i); })
      .attr("stroke", function(d, i) { return rgb(i); })
      .attr("d", area);
  }

  function redraw() {
    var max = Math.max(d3.max(data[0]), d3.max(data[1]), d3.max(data[2]));
    y.domain([0, max]);
    histo.data(data)
      .transition()
      .duration(1000)
      .attr("d", area);
  }

  draw();
}

document.addEventListener('DOMContentLoaded', function() {
  var image = new Image();
  image.src = 'l.jpg';
  image.addEventListener("load", load);
});
</script>
</body>
</html>