Negative transformation of an image using Python and OpenCV

# We need cv2 module for image 
# reading and matplotlib module
# for plotting
import cv2
import matplotlib.pyplot as plt
 
img_bgr = cv2.imread('scenary.jpg', 1)
 
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()

import cv2
import matplotlib.pyplot as plt


# Read an image
img_bgr = cv2.imread('scenary.jpg', 1)
plt.imshow(img_bgr)
plt.show()

# Histogram plotting of the image
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)
    
    # Limit X - axis to 256
    plt.xlim([0, 256])
    
plt.show()

# get height and width of the image
height, width, _ = img_bgr.shape

for i in range(0, height - 1):
    for j in range(0, width - 1):
        
        # Get the pixel value
        pixel = img_bgr[i, j]
        
        # Negate each channel by 
        # subtracting it from 255
        
        # 1st index contains red pixel
        pixel[0] = 255 - pixel[0]
        
        # 2nd index contains green pixel
        pixel[1] = 255 - pixel[1]
        
        # 3rd index contains blue pixel
        pixel[2] = 255 - pixel[2]
        
        # Store new values in the pixel
        img_bgr[i, j] = pixel

# Display the negative transformed image
plt.imshow(img_bgr)
plt.show()

# Histogram plotting of the
# negative transformed image
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()

import cv2
import matplotlib.pyplot as plt


# Read an image
img_bgr = cv2.imread('scenary.jpg', 1)

plt.imshow(img_bgr)
plt.show()

# Histogram plotting of original image
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)
    
    # Limit X - axis to 256
    plt.xlim([0, 256])
    
plt.show()

# Negate the original image
img_neg = 1 - img_bgr

plt.imshow(img_neg)
plt.show()

# Histogram plotting of
# negative transformed image
color = ('b', 'g', 'r')

for i, col in enumerate(color):
    
    histr = cv2.calcHist([img_neg],
                         [i], None, 
                         [256],
                         [0, 256])
    
    plt.plot(histr, color = col)
    plt.xlim([0, 256])
    
plt.show()