opencv 12 adjust contrast

original image, contrast = 0

increased contrast to 5

#main.py

import numpy as np

import cv2

cap = cv2.VideoCapture("assets/Santa Barbara.mp4")

brightness = 50

contrast = 0

trackbars_img = np.uint8(np.full((50, 500, 3), 255))

cv2.imshow('trackbars', trackbars_img)

def brightness_change(x):

    global brightness

    brightness = x

def contrast_change(x):

    global contrast

    contrast = x

cv2.createTrackbar('Brightness', 'trackbars', 50, 100, brightness_change)

cv2.createTrackbar('Contrast', 'trackbars', 0, 10, contrast_change)

while True:

    ret, frame = cap.read()

    width = int(cap.get(3))

    height = int(cap.get(4))

    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

    h, s, v = cv2.split(hsv)

    brightness_adjuster = int((brightness - 50) / 50 * 255)

    #print(brightness_adjuster)

    v_int16 = np.int16(v) + brightness_adjuster

    v_int16[v_int16 > 255] = 255

    v_int16[v_int16 < 0] = 0

    #print(v_int16)

    v = np.uint8(v_int16)

    #print(v)

    final_hsv = cv2.merge((h, s, v))

    image = cv2.cvtColor(final_hsv, cv2.COLOR_HSV2BGR)

    #cv2.imshow('frame', image)

    lab = cv2.cvtColor(image, cv2.COLOR_BGR2LAB)

    #cv2.imshow('lab', lab)

    l, a, b = cv2.split(lab)

    #cv2.imshow('l_channel', l)

    #cv2.imshow('a_channel', a)

    #cv2.imshow('b_channel', b)

    clahe = cv2.createCLAHE(clipLimit=0.01 + contrast, tileGridSize=(8, 8))

    cl = clahe.apply(l)

    #cv2.imshow('CLAHE output', cl)

    limg = cv2.merge((cl, a, b))

    #cv2.imshow('limg', limg)

    final = cv2.cvtColor(limg, cv2.COLOR_LAB2BGR)

    cv2.imshow('frame', final)

    if cv2.waitKey(1) == ord('q'):

        break

    if cv2.waitKey(1) == ord('p'):

        # wait until any key is pressed

        cv2.waitKey(-1)

cap.release()

cv2.destroyAllWindows()

reference:

http://chuanshuoge2.blogspot.com/2021/03/opencv-11-trackbar-adjust-brightness.html

differences between saturation and contrast

Contrast is the difference between light and dark.

Saturation is the intensity of color.

https://www.quora.com/What-are-the-differences-between-saturation-and-contrast-in-photography

adjust contrast

https://stackoverflow.com/questions/39308030/how-do-i-increase-the-contrast-of-an-image-in-python-opencv

CIELAB color

https://en.wikipedia.org/wiki/CIELAB_color_space

CLAHE and Thresholding

https://towardsdatascience.com/clahe-and-thresholding-in-python-3bf690303e40