Calculate the true distance between two points of a DICOM image using Python implementation

import numpy as np
import cv2
import math
import pydicom
from pydicom.pixel_data_handlers.util import convert_color_space

ds = ("./your_dicom_path.dcm")
# The first few charts, dtype defined by Bits Allocated
img = (ds.pixel_array[0], dtype='uint8')
# Getting the color space
color_space = (0x00280004).value
# Color space conversion
img = convert_color_space(img, color_space, 'RGB')
# BGR to RGB
img = (img, cv2.COLOR_BGR2RGB)

# Pixels and real space scales
autio_x = (0x00280030).value[0]
autio_y = (0x00280030).value[1]

p1 = None
p2 = None

# European stock theorem
def cal_euler(p1, p2):
    a2 = ((p2[1] - p1[1]) * autio_x) ** 2
    b2 = ((p2[0] - p1[0]) * autio_y) ** 2
    res = (a2 + b2)
    return res

# Mouse events
def mouseHandler(event, x, y, flags, param):
    global p1, p2
    if event == cv2.EVENT_LBUTTONDOWN:
        point = (x, y)
        if p1 == None:
            p1 = point
        else:
            p2 = point
        print(point)
        ()

('p1')
('p1', mouseHandler)
('p1', img)
()

('p2')
('p2', mouseHandler)
('p2', img)
()

res = cal_euler(p1, p2)

img = (img, p1, p2, (0, 0, 255), 1, 1)
(img, str(round(res, 2)) + "mm", p2, cv2.FONT_HERSHEY_SIMPLEX, 0.7, (0, 0, 255), 1, cv2.LINE_AA)
('res', img)
()