prva

import cv2
import numpy as np
from matplotlib import pyplot as plt

def contrast_stretch_image(img,points):
    rows,cols=img.shape
    img1=(img[0:]).copy()
    for i in range(0,rows):
        for j in range(0,cols):
            value=img[i][j]
            k=1
            while k<len(points):
                (x2,y2)=points[k]
                (x1,y1)=points[k-1]
                if value>=x1 and value<=x2:
                    img1[i][j]=((y2-y1)/(x2-x1))*(value-x1)+y1
                    break

                k+=1
    return img1


img=cv2.imread('slika.png',0)
img_after=contrast_stretch_image(img,([0,0],[50,30],[130,200],[150,220],[256,256]))
plt.figure(1)
plt.subplot(121)
plt.imshow(img,cmap='gray')
plt.title("Original image")
plt.xticks([])
plt.yticks([])
plt.subplot(122)
plt.imshow(img_after,cmap='gray')
plt.title("Image after contrast stretching")
plt.xticks([])
plt.yticks([])
plt.show()