Originally published on https://dev.to/bilal_io/website-screenshots-with-selenium-in-python-kcn

Update 01/01/2019

Here is a Node.js app doing the same work, it is using a React front-end. Node.js App with Selenium and React

Update 12/26/2018

If you wish to run the job using Headless Chrome, either on Windows, Mac, Linux (Desktop or through SSH), I have added a new section at the end of the post.

Original Post

A not too long story short I dread doing repeated tasks manually and that's why I'd rather spend minutes (hours when doing it for the first time) to write a script that automates the process for me. Otherwise I cannot focus, and if you're also horrible at focusing just like I am, I recommend reading Deep Work by Cal Newport.

Problem:

I have a Photoshop mock-up of a laptop, tablet and a phone that I need to use to showcase a website.

That's an easy and quick job, 3 screenshots and 2 minutes later, you're done. But what if you have 10, 20, or 100 websites, and you have to supply screenshots of different screen sizes (a desktop, a mobile and a tablet)?

Solution:

Selenium is the solution. And since I've only used it with Python, I did this tutorial with Python, it is also faster for me to setup compared to a Node.js project, but the functionality should be similar.

Let's start:

If you don't have Python installed in your system already, get it from here: Python 3.6+ You will also need Chrome Webdriver

Once you have Python setup, install Selenium by running the command:

$ pip install selenium

It's easy to get started with python, all you need is a single file that imports the modules you will use, selenium and perhaps time which will allow us to delay/wait a few seconds after the page is loaded before we take the screenshot.

We will also make use of the time module, which is part of the Python standard library..

Next, Create a file with the extension .py and open it with your favorite editor.

First we'll start by importing webdriver from selenium and time.

from selenium import webdriver
import time

Now let's define a list of links we want to take screenshots of

links = ['dev.to', 'twitter.com', 'github.com']

It's import to note that the webdriver does not consider the links above as valid since they do not have the https:// protocol. We will add it later, and the reason I added them without the protocol is so I can use the above as file names.

We can start using the webdriver by calling webdrive.chrome(/path/to/chromedriver) as follows

with webdriver.Chrome("C:/chromedriver_win32/chromedriver") as driver:
    # code goes here using driver

The above reads as with this function defined as driver.. do things with driver Which is equivalent to

driver = webdriver.Chrome("C:/chromedriver_win32/chromedriver")
# code goes here using driver

As far as I can tell, the difference is that the first method will automatically close the browser once it is done doing its job, unlike the second one, which you would have to explicitly call driver.close() to close the browser. If anyone knows other reasons, please let me know in the comments.

For this tutorial I will use the first method. For those new to Python, it is important to note that the following lines will be indented, as they're contained in the statement above, similar to how you would use curly braces to contain a function/class body in C++, JavaScript and other languages.

For the purpose of taking a screenshot, we will use 3 commands: set_window_size(), get() and save_screenshot()

driver.set_window_size(width, height) # takes two arguments, width and height of the browser and it has to be called before using get()
driver.get(url) # takes one argument, which is the url of the website you want to open
driver.save_screenshot(/output-dir/file_name.png) # this one takes one argument which is the path and filename all concatenated. Important: the filename should end with .png

To learn more about these commands head to the Webdriver API documentation

Let's put it all together, we will need to loop through the list of links we created above, and define some variables to use for filename, width and height, and the link with the https:// protocol

with webdriver.Chrome("C:/chromedriver_win32/chromedriver") as driver:
    for link in links:
        desktop = {'output': str(link) + '-desktop.png',
                   'width': 2200,
                   'height': 1800}
        tablet = {'output': str(link) + '-tablet.png',
                  'width': 1200,
                  'height': 1400}
        mobile = {'output': str(link) + '-mobile.png',
                  'width': 680,
                  'height': 1200}
        linkWithProtocol = 'https://' + str(link)

We have defined 3 dictionaries that contain the output filename, width and height for every screen size we need, you can change the dimensions based on your needs.

Now we can start using the commands explained above

# set the window size for desktop
        driver.set_window_size(desktop['width'], desktop['height'])
        driver.get(linkWithProtocol)
        time.sleep(s)
        driver.save_screenshot(desktop['output'])

Noticed that we have used time.sleep(1), what that means is that we asked python to delay the execution of the next line until 2 seconds pass. Even without the sleep command, the driver will wait for the page to fully load before it takes the screenshot, however, if you have any animation, wait for things to settle down, if that's not needed, then you can get rid of the line.

and this is how the tablet and mobile will look like:

# set the window size for tablet
        driver.set_window_size(tablet['width'], tablet['height'])
        driver.get(linkWithProtocol)
        time.sleep(2)
        driver.save_screenshot(tablet['output'])

        # set the window size for mobile
        driver.set_window_size(mobile['width'], mobile['height'])
        driver.get(linkWithProtocol)
        time.sleep(2)
        driver.save_screenshot(mobile['output'])

And with that, all you need to do is run the script from the command line

python script.py

This will open Chrome browser, resize it, take the screenshot each time and output the file at the same directory you have script.py until it is done.

You can be find the code here on Github

Last note

Selenium is capable of great things, it can manipulate pages with CSS and JavaScript, fill out forms and submit them, etc... Learn it and put it to good use.

How to use Selenium with Headless Chrome

It can be annoying to have the browser open and close so many times while you're trying to finish other work. The solution is to use Headless Chrome.

Not much will change from the code above. We need to define our ChromeOptions() and add an argument to it using add_argument() command:

options = webdriver.ChromeOptions() # define options
options.add_argument("headless") # pass headless argument to the options

Then we will pass a new argument to the command we defined before:

with webdriver.Chrome("C:/chromedriver_win32/chromedriver") as driver:
    # code here

becomes

with webdriver.Chrome("C:/chromedriver_win32/chromedriver", chrome_options=options) as driver:
    # code here

This is all you will need for Mac and Windows which I have tested. Linux desktop have not been tested, but I believe it will work.

Linux Server through SSH

Things work differently between Linux Desktop and Server, the latter has no screen, and I am sure it is stripped from so many drivers it does not need, and for that reason, we will have to pass a few more arguments to make it work. As I have not tested this on Linux Desktop, if the solution above does not work, then treat it like we will treat Linux Server

First install Chrome Browser (I never thought I'd need it here)

sudo apt-get install -y chromium-browser # BTW I use Ubuntu (says a non-Arch user)

Then we add these arguments

options = webdriver.ChromeOptions() # define options
options.add_argument("headless") # pass headless argument to the options
options.binary_location = '/usr/bin/chromium-browser' # location of the Chrome Browser binary
options.add_argument("disable-infobars") # disabling infobars
options.add_argument("--disable-extensions") # disabling extensions
options.add_argument("--disable-gpu") # applicable to windows os only
options.add_argument("--disable-dev-shm-usage") # overcome limited resource problems
options.add_argument("--no-sandbox") # Bypass OS security model
# thanks to https://stackoverflow.com/a/50642913/2291648, this answer helped debug the issue

And just like we did above, pass the chrome_options=options to the webdriver.Chrome(...,webdriver.Chrome) as a second argument.

This worked for me, and I hope it does for you.

Github link (updated repo)