fetch.rb

require 'google-search'
require 'uri'
require 'open-uri'
require 'fileutils'

FileUtils.mkdir("images")

Google::Search::Image.new(query: 'High Quality').each do |image|
  name = File.basename(URI.parse(image.uri).path)
  path = File.join("images", name)
  puts name

  begin
    open(path, 'wb') do |file|
      file << open(image.uri, read_timeout: 5).read
    end
  rescue
    puts "failed."
    FileUtils.rm(path)
  end
end

resize.rb

require 'oil'
require 'sinatra'

set :server, 'puma'

get '/' do
  Dir.glob('images/*.jpg').map do |i|
    %Q{<p>#{i}</p><img src="#{i}?w=700&h=500" />}
  end
end

get '/images/*.jpg' do
  content_type :jpeg
  io = File.new(".#{request.path_info}", 'rb')
  cache_control :none
  [200, Oil.new(io, params[:w].to_i, params[:h].to_i)]
end

helpers do
  def img_url(path, width, height)
    "/images/#{path}?w=#{width}&h=#{height}"
  end
end