Add a color manipulation example

2015-10-17 11:53:57 -06:00
parent df6b90246a
commit ecdbab40ba
4 changed files with 209 additions and 1 deletions
@@ -0,0 +1,173 @@
+// NOCOMPILE
+goog.require('ol.Map');
+goog.require('ol.View');
+goog.require('ol.layer.Image');
+goog.require('ol.source.Raster');
+goog.require('ol.source.Stamen');
+
+
+/**
+ * Color manipulation functions below are adapted from
+ * https://github.com/d3/d3-color.
+ */
+var Xn = 0.950470;
+var Yn = 1;
+var Zn = 1.088830;
+var t0 = 4 / 29;
+var t1 = 6 / 29;
+var t2 = 3 * t1 * t1;
+var t3 = t1 * t1 * t1;
+var twoPi = 2 * Math.PI;
+
+
+/**
+ * Convert an RGB pixel into an HCL pixel.
+ * @param {ol.raster.Pixel} pixel A pixel in RGB space.
+ * @return {ol.raster.Pixel} A pixel in HCL space.
+ */
+function rgb2hcl(pixel) {
+  var red = rgb2xyz(pixel[0]);
+  var green = rgb2xyz(pixel[1]);
+  var blue = rgb2xyz(pixel[2]);
+
+  var x = xyz2lab(
+      (0.4124564 * red + 0.3575761 * green + 0.1804375 * blue) / Xn);
+  var y = xyz2lab(
+      (0.2126729 * red + 0.7151522 * green + 0.0721750 * blue) / Yn);
+  var z = xyz2lab(
+      (0.0193339 * red + 0.1191920 * green + 0.9503041 * blue) / Zn);
+
+  var l = 116 * y - 16;
+  var a = 500 * (x - y);
+  var b = 200 * (y - z);
+
+  var c = Math.sqrt(a * a + b * b);
+  var h = Math.atan2(b, a);
+  if (h < 0) {
+    h += twoPi;
+  }
+
+  pixel[0] = h;
+  pixel[1] = c;
+  pixel[2] = l;
+
+  return pixel;
+}
+
+
+/**
+ * Convert an HCL pixel into an RGB pixel.
+ * @param {ol.raster.Pixel} pixel A pixel in HCL space.
+ * @return {ol.raster.Pixel} A pixel in RGB space.
+ */
+function hcl2rgb(pixel) {
+  var h = pixel[0];
+  var c = pixel[1];
+  var l = pixel[2];
+
+  var a = Math.cos(h) * c;
+  var b = Math.sin(h) * c;
+
+  var y = (l + 16) / 116;
+  var x = isNaN(a) ? y : y + a / 500;
+  var z = isNaN(b) ? y : y - b / 200;
+
+  y = Yn * lab2xyz(y);
+  x = Xn * lab2xyz(x);
+  z = Zn * lab2xyz(z);
+
+  pixel[0] = xyz2rgb(3.2404542 * x - 1.5371385 * y - 0.4985314 * z);
+  pixel[1] = xyz2rgb(-0.9692660 * x + 1.8760108 * y + 0.0415560 * z);
+  pixel[2] = xyz2rgb(0.0556434 * x - 0.2040259 * y + 1.0572252 * z);
+
+  return pixel;
+}
+
+function xyz2lab(t) {
+  return t > t3 ? Math.pow(t, 1 / 3) : t / t2 + t0;
+}
+
+function lab2xyz(t) {
+  return t > t1 ? t * t * t : t2 * (t - t0);
+}
+
+function rgb2xyz(x) {
+  return (x /= 255) <= 0.04045 ? x / 12.92 : Math.pow((x + 0.055) / 1.055, 2.4);
+}
+
+function xyz2rgb(x) {
+  return 255 * (x <= 0.0031308 ?
+      12.92 * x : 1.055 * Math.pow(x, 1 / 2.4) - 0.055);
+}
+
+var raster = new ol.source.Raster({
+  sources: [new ol.source.Stamen({
+    layer: 'watercolor'
+  })],
+  operation: function(pixels, data) {
+    var hcl = rgb2hcl(pixels[0]);
+
+    var h = hcl[0] + Math.PI * data.hue / 180;
+    if (h < 0) {
+      h += twoPi;
+    } else if (h > twoPi) {
+      h -= twoPi;
+    }
+    hcl[0] = h;
+
+    hcl[1] *= (data.chroma / 100);
+    hcl[2] *= (data.lightness / 100);
+
+    return hcl2rgb(hcl);
+  },
+  lib: {
+    rgb2hcl: rgb2hcl,
+    hcl2rgb: hcl2rgb,
+    rgb2xyz: rgb2xyz,
+    lab2xyz: lab2xyz,
+    xyz2lab: xyz2lab,
+    xyz2rgb: xyz2rgb,
+    Xn: Xn,
+    Yn: Yn,
+    Zn: Zn,
+    t0: t0,
+    t1: t1,
+    t2: t2,
+    t3: t3,
+    twoPi: twoPi
+  }
+});
+
+raster.on('beforeoperations', function(event) {
+  var data = event.data;
+  for (var id in controls) {
+    data[id] = Number(controls[id].value);
+  }
+});
+
+var map = new ol.Map({
+  layers: [
+    new ol.layer.Image({
+      source: raster
+    })
+  ],
+  target: 'map',
+  view: new ol.View({
+    center: [0, 2500000],
+    zoom: 2,
+    maxZoom: 18
+  })
+});
+
+var controlIds = ['hue', 'chroma', 'lightness'];
+var controls = {};
+controlIds.forEach(function(id) {
+  var control = document.getElementById(id);
+  var output = document.getElementById(id + 'Out');
+  control.addEventListener('input', function() {
+    output.innerText = control.value;
+    raster.changed();
+  });
+  output.innerText = control.value;
+  controls[id] = control;
+});