Scrapes img alt tags from HTML using Ruby with Nokogiri gem

Img Alt Tag Scraper using Nokogiri

require 'nokogiri'
require 'open-uri'

#Scrapes img alt tags from specified URL 
url = "CHANGE ME"
alt_tags = Array.new
doc = Nokogiri::HTML(open(url))
alt_tags = doc.css('img').map{ |i| i['alt'] } 

#Prints out unique alt tags 
puts alt_tags.uniq