k4a camera intrinsics

camera_intrinsics.py

import os
import json
import numpy as np


class Intrinsics(object):
    def __init__(self, json_file):
        assert os.path.isfile(json_file), f'{json_file=} not found'
        with open(json_file, 'r') as f:
            intrinsics_data = json.load(f)
        
        if 'CalibrationInformation' in intrinsics_data:
            self._intrinsics_data = Intrinsics.k4a_intrinsics(intrinsics_data)
            
        # turn it back into arrays
        self._intrinsics_data = {k: np.array(v) for k, v in intrinsics_data.items()}
    
    
    def __get_item__(self, key):
        assert key in self._intrinsics_data, f'{key=} not in _intrinsics_data'
        return self._intrinsics_data[key]
    
    
    @staticmethod
    def k4a_intrinsics(k4a_json_data):
        """ cf: https://github.com/microsoft/Azure-Kinect-Sensor-SDK/blob/develop/examples/calibration_registration/camera_tools.py#L151
        intrinsics = [camera_matrix[0][2]/img_size[0][0], #Px
        camera_matrix[1][2]/img_size[1][0], #Py
        camera_matrix[0][0]/img_size[0][0], #Fx
        camera_matrix[1][1]/img_size[1][0], #Fy
        dist[0][0], #K1
        dist[1][0], #K2
        dist[4][0], #K3
        dist[5][0], #K4
        dist[6][0], #K5
        dist[7][0], #K6
        0, #Cx always Zero. (BrownConrady)
        0, #Cy always Zero. (BrownConrady)
        dist[3][0], #P2/Tx
        dist[2][0]] #P1/Ty
        """
        bc_model_parameters = k4a_json_data['CalibrationInformation']['Cameras'][1]['Intrinsics']['ModelParameters']