how to change file download location in Webdriver while using chrome driver/firefox driver

I am trying to save an image by using save as option inside a specific folder. I found a way by which i am able to right click on the image which i want to save using save as option. But the problem where i am stuck is after getting the os window which asks where to save the file i am not able to send the desired location because i don't know how to do it. I went through the similar questions asked on this forum but non of them helped so far.

Code is-

For Firefox-

public class practice {



 public void pic() throws AWTException{

     WebDriver driver;



     //Proxy Setting     

        FirefoxProfile profile = new FirefoxProfile();

        profile.setAssumeUntrustedCertificateIssuer(false);

        profile.setEnableNativeEvents(false);

        profile.setPreference("network.proxy.type", 1);

        profile.setPreference("network.proxy.http", "localHost");

        profile.setPreference("newtwork.proxy.http_port",3128);



        //Download setting

        profile.setPreference("browser.download.folderlist", 2);

        profile.setPreference("browser.helperapps.neverAsk.saveToDisk","jpeg");

        profile.setPreference("browser.download.dir", "C:\\Users\\Admin\\Desktop\\ScreenShot\\pic.jpeg");

        driver = new FirefoxDriver(profile);



        driver.navigate().to("http://stackoverflow.com/users/2675355/shantanu");

        driver.findElement(By.xpath("//*[@id='large-user-info']/div[1]/div[1]/a/div/img"));

        Actions action = new Actions(driver);

        action.moveToElement(driver.findElement(By.xpath("//*[@id='large-user-info']/div[1]/div[1]/a/div/img"))).perform();

        action.contextClick().perform();

        Robot robo = new Robot();

        robo.keyPress(KeyEvent.VK_V);

        robo.keyRelease(KeyEvent.VK_V);

    // Here i am getting the os window but don't know how to send the desired location

    }//method   

}//class

public class practice {

   public void s() throws AWTException{

        WebDriver driver;   

        System.setProperty("webdriver.chrome.driver","C:\\Users\\Admin\\Desktop\\chromedriver.exe");

        driver = new ChromeDriver();

        driver.navigate().to("http://stackoverflow.com/users/2675355/shantanu");

        driver.findElement(By.xpath("//*[@id='large-user-info']/div[1]/div[1]/a/div/img"));

        Actions action = new Actions(driver);

        action.moveToElement(driver.findElement(By.xpath("//*[@id='large-user-info']/div[1]/div[1]/a/div/img"))).perform();

        action.contextClick().perform();

        Robot robo = new Robot();

        robo.keyPress(KeyEvent.VK_V);

        robo.keyRelease(KeyEvent.VK_V);

        // Here i am getting the os window but don't know how to send the desired location

   }

 }