cubemap_to_equirec.py

from typing import List
import numpy as np
import cv2


def cubemap_to_equirec(cubefaces: List[np.ndarray]) -> np.ndarray:
    """Convert a list of cubefaces (FRBLUD) into an equirectangular image"""
    # Stack cubefaces horizontally
    cubemap = np.hstack(cubefaces)

    # Set the width of the output image to a multiple of 8
    face_size = cubemap.shape[0]
    out_height = (int(face_size * np.pi) // 8) * 4
    out_width = out_height * 2

    # XY maps
    frbl_x, frbl_y = get_frbl_maps(out_width, out_height, face_size)
    ud_x, ud_y = get_ud_maps(out_width, out_height, face_size)

    # Combine
    ceiling = get_up_mask(out_height, out_width).astype(np.float32)
    ceiling += np.flipud(ceiling)
    map_x = ceiling*ud_x + (1-ceiling)*frbl_x
    map_y = ceiling*ud_y + (1-ceiling)*frbl_y

    # Opencv shift
    map_x -= 0.5
    map_y -= 0.5
        
    return cv2.remap(cubemap, map_x, map_y, cv2.INTER_CUBIC,
                     borderMode=cv2.BORDER_REPLICATE)