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   "source": [
    "from openpiv.pyprocess import extended_search_area_piv as piv\n",
    "\n",
    "import numpy as np\n",
    "\n",
    "\n",
    "from skimage.util import random_noise\n",
    "from skimage import img_as_ubyte\n",
    "\n",
    "threshold = 0.1\n",
    "shift_u = -5\n",
    "shift_v = 4\n",
    "\n",
    "\n",
    "def dist(u, shift):\n",
    "    return np.mean(np.abs(u - shift))\n",
    "\n",
    "def create_pair(image_size=32, u=shift_u, v=shift_v):\n",
    "    \"\"\" creates a pair of images with a roll/shift \"\"\"\n",
    "    frame_a = np.zeros((image_size, image_size))\n",
    "    frame_a = random_noise(frame_a)\n",
    "    frame_a = img_as_ubyte(frame_a)\n",
    "    # note rolling positive vertical +2 means we create\n",
    "    # negative vertical velocity as our origin is at 0,0\n",
    "    # bottom left corner, and the image is rolled from the\n",
    "    # top left corner\n",
    "\n",
    "    frame_b = np.roll(np.roll(frame_a, u, axis=1), v, axis=0)\n",
    "    return frame_a.astype(np.int32), frame_b.astype(np.int32)\n",
    "\n",
    "def test_piv():\n",
    "    \"\"\"test of the simplest PIV run\n",
    "    default window_size = 32\n",
    "    \"\"\"\n",
    "    frame_a, frame_b = create_pair(image_size=64)\n",
    "    u, v = piv(frame_a, frame_b, window_size=64)\n",
    "    print(u,v)\n",
    "    assert dist(u, shift_u) < threshold\n",
    "    assert dist(v, -shift_v) < threshold\n",
    "\n",
    "def test_piv_smaller_window():\n",
    "    \"\"\" test of the search area larger than the window \"\"\"\n",
    "    frame_a, frame_b = create_pair(image_size=32, u=-3, v=-2)\n",
    "    u, v = piv(frame_a, frame_b, window_size=16, search_area_size=32)\n",
    "    assert dist(u, -3) < threshold\n",
    "    assert dist(v, 2) < threshold\n",
    "\n",
    "def test_extended_search_area():\n",
    "    \"\"\" test of the extended area PIV with larger image \"\"\"\n",
    "    frame_a, frame_b = create_pair(image_size=64)\n",
    "    u, v = piv(frame_a, frame_b,\n",
    "               window_size=16, search_area_size=32, overlap=0)\n",
    "\n",
    "    assert (dist(u, shift_u) + dist(v, -shift_v)) < 2 * threshold\n",
    "\n",
    "def test_extended_search_area_overlap():\n",
    "    \"\"\" test of the extended area PIV with different overlap \"\"\"\n",
    "    frame_a, frame_b = create_pair(image_size=64)\n",
    "    u, v = piv(frame_a, frame_b,\n",
    "               window_size=16, search_area_size=32, overlap=8)\n",
    "    assert (dist(u, shift_u) + dist(v, -shift_v)) < 2 * threshold\n",
    "\n",
    "def test_extended_search_area_sig2noise():\n",
    "    \"\"\" test of the extended area PIV with sig2peak \"\"\"\n",
    "    frame_a, frame_b = create_pair(image_size=64)\n",
    "    u, v, s2n = piv(\n",
    "        frame_a,\n",
    "        frame_b,\n",
    "        window_size=16,\n",
    "        search_area_size=32,\n",
    "        sig2noise_method=\"peak2peak\",\n",
    "    )\n",
    "    assert (dist(u, shift_u) + dist(v, -shift_v)) < 2 * threshold\n",
    "\n",
    "def test_process_extended_search_area():\n",
    "    \"\"\" test of the extended area PIV from Cython \"\"\"\n",
    "    frame_a, frame_b = create_pair(image_size=64)\n",
    "    u, v = piv(frame_a, frame_b, window_size=16, search_area_size=32, dt=1, overlap=0)\n",
    "    # assert(np.max(np.abs(u[:-1,:-1]-3)+np.abs(v[:-1,:-1]+2)) <= 0.3)\n",
    "    assert (dist(u, shift_u) + dist(v, -shift_v)) < 2 * threshold"
   ]
  }
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