Jupyter/parse_ASP_Tsai_camera_calibration_files.ipynb

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    "## <div align=\"center\">Parse ASP Tsai camera calibration files</div> ##\n",
    "\n",
    "This notebook parses an ASP camera calibration file using the Tsai camera calibration technique, extract parameters, and returns a class with the extracted values that were found.\n",
    "\n",
    "Parameters include focal lengths $f_{u, v}$, radial ($k_{1, 2}$) and tangential ($p_{1, 2}$) lens distortion parameters (see: [ASP frame camera models](https://stereopipeline.readthedocs.io/en/latest/pinholemodels.html)) and others.\n",
    "\n",
    "A Python™ version of the code is available at [Parse ASP camera calibration files using the TSAI distortion model](https://github.com/mstudinger/ATM-SfM-Bathymetry/blob/main/Python/parse_ASP_TSAI_camera_calibration_files.py)."
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     "text": [
      "Prosilica GT 4905C camera with Zeiss 28 mm/F2 lens (S/N 51500462)\n",
      "                      Focal length estimates                     \n",
      "-----------------------------------------------------------------\n",
      "fu = 28.37 mm\n",
      "fv = 27.98 mm\n",
      "\n",
      "                 Center/principal point estimates                \n",
      "-----------------------------------------------------------------\n",
      "cu = 2447.50 pixels\n",
      "cv = 1631.50 pixels\n"
     ]
    }
   ],
   "source": [
    "# import required modules\n",
    "import re\n",
    "\n",
    "def parse_asp_tsai_file(\n",
    "    f_name:str,   # ASP camera calibration file using the Tsai camera calibration technique\n",
    "    ) -> object:  # a class containing the extracted parameters that were found\n",
    "\n",
    "    \"\"\"\n",
    "      Parse ASP camera calibration file using the Tsai camera calibration technique,\n",
    "      extract parameters, and return a class with the extracted values that were found.\n",
    "    \"\"\"\n",
    "    \n",
    "    # read camera/lens calibration file for parsing\n",
    "    lens_cal = open(f_name, 'r')\n",
    "    tsai_info = lens_cal.readlines() # reads the entire file\n",
    "    lens_cal.close()\n",
    "    \n",
    "    # define a class TsaiParams for organizing the extracted lens calibration parameters\n",
    "    class TsaiParams():\n",
    "        def __init__(self):\n",
    "            self.fu    = None\n",
    "            self.fv    = None\n",
    "            self.cu    = None\n",
    "            self.cv    = None\n",
    "            self.k1    = None\n",
    "            self.k2    = None\n",
    "            self.p1    = None\n",
    "            self.p2    = None\n",
    "            self.pitch = None\n",
    "    \n",
    "    # create return variable \"tsai_params\" as a TsaiParams class\n",
    "    tsai_params = TsaiParams()\n",
    "    \n",
    "    # the code for parsing the lens calibration files was inspired \n",
    "    # by C. Wayne Wright's (https://github.com/lidar532) function:\n",
    "    # parse_cambot_header in the Jupyter notebook:\n",
    "    # https://github.com/mstudinger/ATM-SfM-Bathymetry/blob/main/Jupyter/CAMBOTv2_convert_GPS_to_camera_pos.ipynb\n",
    "    \n",
    "    # define search patterns and group names\n",
    "    # to develop/verify search patterns with https://regex101.com/ make sure to select\n",
    "    # Python™ in the \"FLAVOR\" tab on the left and then use the string inside r\"\":\n",
    "    rx_fu = r\"fu = (?P<fu>.\\d*\\.*\\d*)\" \n",
    "    rx_fv = r\"fv = (?P<fv>.\\d*\\.*\\d*)\"\n",
    "    rx_cu = r\"cu = (?P<cu>.\\d*\\.*\\d*)\"\n",
    "    rx_cv = r\"cv = (?P<cv>.\\d*\\.*\\d*)\"\n",
    "    rx_k1 = r\"k1 = (?P<k1>.\\d*\\.*\\d*)\" # includes positive and negative values\n",
    "    rx_k2 = r\"k2 = (?P<k2>.\\d*\\.*\\d*)\"\n",
    "    rx_p1 = r\"p1 = (?P<p1>.\\d*\\.*\\d*)\"\n",
    "    rx_p2 = r\"p2 = (?P<p2>.\\d*\\.*\\d*)\"\n",
    "    \n",
    "    # read pitch value. if pitch = 1.0 units for focal length etc. are in pixels\n",
    "    rx_pitch = r\"pitch = (?P<pitch>.\\d*\\.*\\d*)\"  \n",
    "    \n",
    "    for line in tsai_info:\n",
    "        \n",
    "        re_srch = re.search(rx_fu, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.fu = float(re_srch.group('fu'))\n",
    "        \n",
    "        re_srch = re.search(rx_fv, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.fv = float(re_srch.group('fv'))\n",
    "            \n",
    "        re_srch = re.search(rx_cu, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.cu = float(re_srch.group('cu'))        \n",
    "            \n",
    "        re_srch = re.search(rx_cv, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.cv = float(re_srch.group('cv'))        \n",
    "    \n",
    "        re_srch = re.search(rx_k1, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.k1 = float(re_srch.group('k1'))    \n",
    "            \n",
    "        re_srch = re.search(rx_k2, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.k2 = float(re_srch.group('k2'))        \n",
    "    \n",
    "        re_srch = re.search(rx_p1, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.p1 = float(re_srch.group('p1'))    \n",
    "            \n",
    "        re_srch = re.search(rx_p2, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.p2 = float(re_srch.group('p2'))        \n",
    "    \n",
    "        re_srch = re.search(rx_pitch, line, flags=0)\n",
    "        if re_srch:\n",
    "            tsai_params.pitch = float(re_srch.group('pitch'))\n",
    "        \n",
    "    return tsai_params\n",
    "\n",
    "#%% run module/function as script \n",
    "\n",
    "if __name__ == '__main__':\n",
    "    \n",
    "    import os\n",
    "    # set input directory with ASP Tsai camera calibration file for parsing\n",
    "    f_dir_cal = r\"..\" + os.sep + \"data\" + os.sep + \"calibration\"\n",
    "    # set Tsai input file name for parsing\n",
    "    f_name = f_dir_cal + os.sep + \"CAMBOT_28mm_51500462_ASP_cal_pix_mod.tsai\"\n",
    "\n",
    "    # execute function    \n",
    "    tsai_params_asp = parse_asp_tsai_file(f_name)\n",
    "    \n",
    "    # Prosilica GT 4905C camera pixel size is 5.5 μm × 5.5 μm\n",
    "    pixel_mm = 5.5 * 0.001\n",
    "    \n",
    "    # display some example values. center section headlines nicely\n",
    "    horz_line = '-----------------------------------------------------------------'\n",
    "    len_horz_line = len(horz_line)\n",
    "    \n",
    "    str_title = 'Prosilica GT 4905C camera with Zeiss 28 mm/F2 lens (S/N 51500462)'\n",
    "    str_title = str_title.center(len_horz_line, \" \")\n",
    "    str_focal = 'Focal length estimates'\n",
    "    str_focal = str_focal.center(len_horz_line, \" \")\n",
    "       \n",
    "    str_principal = 'Center/principal point estimates'\n",
    "    str_principal = str_principal.center(len_horz_line, \" \")\n",
    "\n",
    "    print(str_title)\n",
    "    print(str_focal)\n",
    "    print(horz_line)\n",
    "    print(f'fu = {tsai_params_asp.fu*pixel_mm:5.2f} mm')\n",
    "    print(f'fv = {tsai_params_asp.fv*pixel_mm:5.2f} mm\\n')\n",
    "    print(str_principal)\n",
    "    print(horz_line)\n",
    "    print(f'cu = {tsai_params_asp.cu:7.2f} pixels')\n",
    "    print(f'cv = {tsai_params_asp.cv:7.2f} pixels')"
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