Lecture 3.14 - Perspective & Affine Transforms.ipynb

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    "\n",
    "## Getting Perpsective Transform"
   ]
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    "import cv2\n",
    "import numpy as np\n",
    "import matplotlib.pyplot as plt\n",
    "\n",
    "image = cv2.imread('images/scan.jpg')\n",
    "\n",
    "cv2.imshow('Original', image)\n",
    "cv2.waitKey(0)\n",
    "\n",
    "# Cordinates of the 4 corners of the original image\n",
    "points_A = np.float32([[320,15], [700,215], [85,610], [530,780]])\n",
    "\n",
    "# Cordinates of the 4 corners of the desired output\n",
    "# We use a ratio of an A4 Paper 1 : 1.41\n",
    "points_B = np.float32([[0,0], [420,0], [0,594], [420,594]])\n",
    " \n",
    "# Use the two sets of four points to compute \n",
    "# the Perspective Transformation matrix, M    \n",
    "M = cv2.getPerspectiveTransform(points_A, points_B)\n",
    " \n",
    "warped = cv2.warpPerspective(image, M, (420,594))\n",
    " \n",
    "cv2.imshow('warpPerspective', warped)\n",
    "cv2.waitKey(0)\n",
    "cv2.destroyAllWindows()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## In affine transforms you only need 3 coordiantes to obtain the correct transform"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "import cv2\n",
    "import numpy as np\n",
    "import matplotlib.pyplot as plt\n",
    "\n",
    "image = cv2.imread('images/ex2.jpg')\n",
    "rows,cols,ch = image.shape\n",
    "\n",
    "cv2.imshow('Original', image)\n",
    "cv2.waitKey(0)\n",
    "\n",
    "# Cordinates of the 4 corners of the original image\n",
    "points_A = np.float32([[320,15], [700,215], [85,610]])\n",
    "\n",
    "# Cordinates of the 4 corners of the desired output\n",
    "# We use a ratio of an A4 Paper 1 : 1.41\n",
    "points_B = np.float32([[0,0], [420,0], [0,594]])\n",
    " \n",
    "# Use the two sets of four points to compute \n",
    "# the Perspective Transformation matrix, M    \n",
    "M = cv2.getAffineTransform(points_A, points_B)\n",
    "\n",
    "warped = cv2.warpAffine(image, M, (cols, rows))\n",
    " \n",
    "cv2.imshow('warpPerspective', warped)\n",
    "cv2.waitKey(0)\n",
    "cv2.destroyAllWindows()"
   ]
  }
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