Extract Bounding Box Coordinates from Image

ExtractBoundingBox

import cv2

class ExtractImageWidget(object):
    def __init__(self):
        self.original_image = cv2.imread('test.png')
        self.clone = self.original_image.copy()

        cv2.namedWindow('image')
        cv2.setMouseCallback('image', self.extract_coordinates)

        # Bounding box reference points and boolean if we are extracting coordinates
        self.image_coordinates = []
        self.extract = False

    def extract_coordinates(self, event, x, y, flags, parameters):
        # Record starting (x,y) coordinates on left mouse button click
        if event == cv2.EVENT_LBUTTONDOWN:
            self.image_coordinates = [(x,y)]
            self.extract = True

        # Record ending (x,y) coordintes on left mouse bottom release
        elif event == cv2.EVENT_LBUTTONUP:
            self.image_coordinates.append((x,y))
            self.extract = False
            print('top left: {}, bottom right: {}'.format(self.image_coordinates[0], self.image_coordinates[1]))
            print('x,y,w,h : ({}, {}, {}, {})'.format(self.image_coordinates[0][0], self.image_coordinates[0][1], self.image_coordinates[1][0] - self.image_coordinates[0][0], self.image_coordinates[1][1] - self.image_coordinates[0][1]))

            # Draw rectangle around ROI
            cv2.rectangle(self.clone, self.image_coordinates[0], self.image_coordinates[1], (0,255,0), 2)
            cv2.imshow("image", self.clone) 
 pic = 1
 while pic = 1:
     cv2.imshow('image', extract_image_widget.show_image())
     key = cv2.waitKey(0)

     # Close program with keyboard 'q'
     if key == ord('q'):
         cv2.destroyAllWindows()
         pic = 0
         exit()
         
cv2.destroyAllWindows()

Credits to @nathancy on Stack Overflow. Minor edits made for context, but major script author is still @nathancy
You can see his response to the question here.
Please check out his Stack Overflow profile here.