PerspectiveTransformation.py

import cv2
import numpy as np

class PerspectiveTransformation:
    """ This a class for transforming image between front view and top view

    Attributes:
        src (np.array): Coordinates of 4 source points
        dst (np.array): Coordinates of 4 destination points
        M (np.array): Matrix to transform image from front view to top view
        M_inv (np.array): Matrix to transform image from top view to front view
    """
    def __init__(self):
        """Init PerspectiveTransformation."""
        self.src = np.float32([(550, 460),     # top-left
                               (150, 720),     # bottom-left
                               (1200, 720),    # bottom-right
                               (770, 460)])    # top-right
        self.dst = np.float32([(100, 0),
                               (100, 720),
                               (1100, 720),
                               (1100, 0)])
        self.M = cv2.getPerspectiveTransform(self.src, self.dst)
        self.M_inv = cv2.getPerspectiveTransform(self.dst, self.src)

    def forward(self, img, img_size=(1280, 720), flags=cv2.INTER_LINEAR):
        """ Take a front view image and transform to top view

        Parameters:
            img (np.array): A front view image
            img_size (tuple): Size of the image (width, height)
            flags : flag to use in cv2.warpPerspective()

        Returns:
            Image (np.array): Top view image
        """
        return cv2.warpPerspective(img, self.M, img_size, flags=flags)

    def backward(self, img, img_size=(1280, 720), flags=cv2.INTER_LINEAR):
        """ Take a top view image and transform it to front view

        Parameters:
            img (np.array): A top view image
            img_size (tuple): Size of the image (width, height)
            flags (int): flag to use in cv2.warpPerspective()

        Returns:
            Image (np.array): Front view image
        """
        return cv2.warpPerspective(img, self.M_inv, img_size, flags=flags)