How to make screenshot for full entire web page, not only partial from the top using Selenium WebDriver?

my Selenium WD java code is as below: System.setProperty("webdriver.chrome.driver","/home/alex/Downloads/chromedriver_linux64/chromedriver");

 WebDriver driver = new ChromeDriver(); driver.get("http://google.com"); File scrFile = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE); FileUtils.copyFile(scrFile, new File(RESULT_FILENAME)); 

any ideas?