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','image')
    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','image')
    img=np.uint8(np.clip((alpha*img2+beta),0,255))
#3
cv.namedWindow('modify_sample')
cv.createTrackbar('Alpha','image',0,300,updateAlpha)
cv.createTrackbar('Beta','image',0,255,updateBeta)
cv.setTrackbarPos('Alpha','image',100)
cv.setTrackbarPos('Beta','image',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)