Display the brightness distribution from input images

brightness_histogram.py

"""
Simple script to check the brightness distribution from images.

Ensure you have opencv and matplotlib installed, via

  pip install opencv-python matplotlib
"""
__author__ = "Thomas Reidemeister <thomas@labforge.ca>"

import sys
import cv2
import matplotlib.pyplot as plt

def plot_histogram(image_path):
    # Read the image
    image = cv2.imread(image_path, cv2.IMREAD_COLOR)

    if image is None:
        print("Could not open or find the image")
        return

    # Convert to grayscale
    gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

    # Calculate the histogram
    hist = cv2.calcHist([gray_image], [0], None, [256], [0, 256])

    # Plot the histogram
    plt.figure()
    plt.title("Grayscale Histogram")
    plt.xlabel("Bins")
    plt.ylabel("# of Pixels")
    plt.plot(hist, color="gray")
    plt.xlim([0, 256])
    plt.legend(['Brightness'])

    # Display the histogram
    plt.show()

if __name__ == '__main__':
    if len(sys.argv) != 2:
        print("Usage <script> <image>", file=sys.stderr)
        sys.exit(1)

    plot_histogram(sys.argv[1])