{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%matplotlib inline\n",
    "import numpy as np\n",
    "import matplotlib.pyplot as plt"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise\n",
    "\n",
    "In the film industry, it is often necessary to impose actors on top of a rendered background.  To do that, the actors are filmed on a \"green screen\".  Here's an example shot (``images/greenscreen.jpg``):\n",
    "\n",
    "<img src=\"skimage/greenscreen.jpg\" width=\"300px\"/>\n",
    "\n",
    "Say we'd like to help these folks travel into a forest (``skimage/forest.jpg``):\n",
    "\n",
    "<img src=\"skimage/forest.jpg\" width=\"300px\"/>\n",
    "\n",
    "Can you transplant the foreground of the greenscreen onto the backdrop of the forest?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from skimage import io\n",
    "\n",
    "forest = io.imread('skimage/forest.jpg')\n",
    "people = io.imread('skimage/greenscreen.jpg')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "forest.shape, people.shape"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "forest = forest[:375, :500, :]\n",
    "\n",
    "from skimage import img_as_float\n",
    "forest = img_as_float(forest)\n",
    "people = img_as_float(people)\n",
    "\n",
    "print(forest.max(), people.max())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "mask = people[..., 1] < 0.7"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.imshow(mask)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "people_selected = people.copy()\n",
    "#people_selected[mask] = 0\n",
    "\n",
    "# Should clean up mask a bit here to fill all the holes\n",
    "from skimage import morphology\n",
    "mask = morphology.binary_closing(mask, morphology.selem.disk(15))\n",
    "#mask = morphology.binary_erosion(mask, morphology.selem.disk(5))\n",
    "\n",
    "plt.imshow(mask)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "forest_with_ppl = forest.copy()\n",
    "forest_with_ppl[mask] = people[mask]\n",
    "\n",
    "plt.imshow(forest_with_ppl)"
   ]
  }
 ],
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