import numpy as np
import cv2

img=cv2.imread('images/low_contrast_1.jpg',cv2.IMREAD_GRAYSCALE)

height=img.shape[0]
width=img.shape[1]

min=255
max=0

for i in np.arange(height):
        for j in np.arange(width):
            a=img.item(i,j)
            if a>max:
                max=a
            if a<min:
                min=a
for i in np.arange(height):
    for j in np.arange(width):
        a=img.item(i,j)
        b=float(a-min)/(max-min)*255
        img.itemset((i,j),b)
            
cv2.imwrite('images/auto_contrast.jpg',img)
cv2.imshow('image',img)
cv2.waitKey(0)
cv2.destroyAllWindows()