A simple IPython widget to interactively design an Hcl colormap

interactive_colormap_chooser.ipynb

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  {
   "cell_type": "markdown",
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   "source": [
    "\n",
    "# Interactive H$_{CL}$ Colormap Designer"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This notebook is based off a proposed system for designing the new default matplotlib colormap proposed [here](http://nbviewer.ipython.org/gist/mwaskom/6a43a3b94eca4a9e2e8b). It generalizes the approach into an interactive IPython widget, so that one can play with the ramps for the three paramters and see in real time what the resulting colormap will look like.\n",
    "\n",
    "Originally written by Michael Waskom, February 18, 2015. Placed in public domain."
   ]
  },
  {
   "cell_type": "code",
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   "metadata": {
    "collapsed": true
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   "outputs": [],
   "source": [
    "%matplotlib inline"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      ":0: FutureWarning: IPython widgets are experimental and may change in the future.\n"
     ]
    }
   ],
   "source": [
    "import numpy as np\n",
    "import matplotlib as mpl\n",
    "import matplotlib.pyplot as plt\n",
    "from IPython.html.widgets import interact, IntRangeSlider, IntSlider"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "from colormath.color_objects import sRGBColor, LCHabColor, LabColor\n",
    "from colormath.color_conversions import convert_color"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def in_gamut(rgb_color):\n",
    "    rgb_vals = np.array(rgb_color.get_value_tuple())\n",
    "    return ((0 < rgb_vals) & (rgb_vals < 1)).all()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "def make_colormap(L_ramp, c_ramp, h_ramp):\n",
    "    rgb_colors = []\n",
    "    gamut_status = []\n",
    "    for L, c, h in zip(L_ramp, c_ramp, h_ramp):\n",
    "        Lch = LCHabColor(L, c, h)\n",
    "        rgb = convert_color(Lch, sRGBColor)\n",
    "        rgb_colors.append((rgb.clamped_rgb_r, rgb.clamped_rgb_g, rgb.clamped_rgb_b))\n",
    "        gamut_status.append(in_gamut(rgb))\n",
    "    cmap = mpl.colors.LinearSegmentedColormap.from_list(\"hcl_colormap\", rgb_colors)\n",
    "    return cmap, gamut_status"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "def plot_colormap(cmap, gamut_status):\n",
    "    f, (ax_cmap, ax_gamut) = plt.subplots(2, figsize=(10, 1), sharex=True,\n",
    "                                          gridspec_kw={\"height_ratios\": (3, 1)})\n",
    "    x = np.linspace(0, 1, 256)\n",
    "    ax_cmap.pcolormesh(np.array([x]), cmap=cmap)\n",
    "    ax_cmap.set_axis_off()\n",
    "\n",
    "    ax_gamut.pcolormesh(np.array(gamut_status)[np.newaxis, :], cmap=\"Greys_r\", vmin=-.5)\n",
    "    ax_gamut.set_axis_off()\n",
    "    ax_gamut.set(xlim=(0, 256))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Here's the widget itself. If you downloaded this notebook, run the cell and you'll see the interactive part. It shows the colormap and then below the colormap it shows where we have strayed out of gamut (assuming I did the calculations right)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
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   "outputs": [
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   "source": [
    "@interact\n",
    "def choose_colormap(\n",
    "        L=IntRangeSlider(min=0, max=100, value=(20, 90), width=450),\n",
    "        c=IntRangeSlider(min=0, max=100, value=(30, 50), width=450),\n",
    "        h_start=IntSlider(min=0, max=360, value=240, width=450),\n",
    "        h_rot=IntSlider(min=-360, max=360, value=210, width=450)\n",
    "        ):\n",
    "    \n",
    "    L_ramp = np.linspace(*L, num=256)\n",
    "    c_ramp = np.linspace(*c, num=256)\n",
    "    h_ramp = np.linspace(h_start, h_start + h_rot, 256) % 360\n",
    "    cmap, gamut_status = make_colormap(L_ramp, c_ramp, h_ramp)\n",
    "    plot_colormap(cmap, gamut_status)"
   ]
  },
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   "execution_count": null,
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