from matplotlib import pyplot as plt

import argparse

import cv2

ap = argparse.ArgumentParser()

ap.add_argument("-i", "--image", required = True,

help = "Path to the image")

args = vars(ap.parse_args())

image = cv2.imread(args["image"])

image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

cv2.imshow("Original", image)

hist = cv2.calcHist([image], [0], None, [256], [0, 256])

plt.figure()

plt.title("Grayscale Histogram")

plt.xlabel("Bins")

plt.ylabel("# of Pixels")

plt.plot(hist)

plt.xlim([0, 256])

plt.show()

cv2.waitKey(0)