Hi Gulzar, to understand how capturing of viewable area of a webpage works, checkout following automation script:
from selenium import webdriver
options = webdriver.ChromeOptions()
options.add_argument('--ignore-certificate-errors')
options.add_argument("--test-type")
options.binary_location = "/usr/bin/chromium"
driver = webdriver.Chrome(chrome_options=options)
driver.get('https://edureka.co')
driver.save_screenshot("screenshot.png")
driver.close()