Negative.py

# Negative
import cv2
import matplotlib.pyplot as plt

img_bgr = cv2.imread('picture1.jpg', 1)
plt.imshow(img_bgr)
plt.show()

color = ('b', 'g', 'r')

for i, col in enumerate(color):
    histr = cv2.calcHist([img_bgr],
                         [i], None,
                         [256],
                         [0, 256])

    plt.plot(histr, color=col)

    plt.xlim([0, 256])

plt.show()

height, width, _ = img_bgr.shape

for i in range(0, height - 1):
    for j in range(0, width - 1):
        pixel = img_bgr[i, j]

        pixel[0] = 255 - pixel[0]

        pixel[1] = 255 - pixel[1]

        pixel[2] = 255 - pixel[2]

        img_bgr[i, j] = pixel

plt.imshow(img_bgr)
plt.show()

color = ('b', 'g', 'r')

for i, col in enumerate(color):
    histr = cv2.calcHist([img_bgr],
                         [i], None,
                         [256],
                         [0, 256])

    plt.plot(histr, color=col)
    plt.xlim([0, 256])

plt.show()