histogram.py

# pylint:disable=no-member

import cv2 as cv
import matplotlib.pyplot as plt
import numpy as np

img = cv.imread("Photos/pic.jpg")
cv.imshow("Cats", img)

blank = np.zeros(img.shape[:2], dtype="uint8")

# gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)
# cv.imshow('Gray', gray)

mask = cv.circle(blank, (img.shape[1] // 2, img.shape[0] // 2), 100, 255, -1)

masked = cv.bitwise_and(img, img, mask=mask)
cv.imshow("Mask", masked)

# GRayscale histogram
# gray_hist = cv.calcHist([gray], [0], mask, [256], [0,256] )

# plt.figure()
# plt.title('Grayscale Histogram')
# plt.xlabel('Bins')
# plt.ylabel('# of pixels')
# plt.plot(gray_hist)
# plt.xlim([0,256])
# plt.show()

# Colour Histogram

plt.figure()
plt.title("Colour Histogram")
plt.xlabel("Bins")
plt.ylabel("# of pixels")
colors = ("b", "g", "r")
for i, col in enumerate(colors):
    hist = cv.calcHist([img], [i], mask, [256], [0, 256])
    plt.plot(hist, color=col)
    plt.xlim([0, 256])

plt.show()

cv.waitKey(0)