import cv2 as cv
import numpy as np

# 1
img = cv.imread("sample.jpg", cv.IMREAD_GRAYSCALE)
img2 = cv.imread('sample.jpg', cv.IMREAD_GRAYSCALE)


# 2
def draw_circle(event, x, y, flags, param):
    if event == cv.EVENT_LBUTTONDOWN:
        cv.circle(img, (x, y), 10, 0, -1)


# 4
alpha = 0.3
beta = 80


def updateAlpha(x):
    global alpha, img, img2
    alpha = cv.getTrackbarPos('Alpha', 'modify_sample')
    alpha = alpha * 0.01
    img = np.uint8(np.clip((alpha * img2 + beta), 0, 255))


def updateBeta(x):
    global beta, img, img2
    beta = cv.getTrackbarPos('Beta', 'modify_sample')
    img = np.uint8(np.clip((alpha * img2 + beta), 0, 255))


# 3
cv.namedWindow('modify_sample')
cv.createTrackbar('Alpha', 'modify_sample', 0, 300, updateAlpha)
cv.createTrackbar('Beta', 'modify_sample', 0, 255, updateBeta)
cv.setTrackbarPos('Alpha', 'modify_sample', 100)
cv.setTrackbarPos('Beta', 'modify_sample', 10)
cv.setMouseCallback('modify_sample', draw_circle)
while (1):
    cv.imshow('modify_sample', img)
    pressedKey = cv.waitKey(5)
    # 5
    if pressedKey == ord('q'):
        break
    if pressedKey == ord('s'):
        cv.imwrite('modified_sample.jpg', img)