this ruby script takes txt file of image post URLs and downloads the images.

download-images-from-tumblr.rb

#!/bin/ruby

require 'open-uri'
require 'tumblr_client'
require 'json'
require 'uri'

#this takes the txt file with the photo post URLs where you're grabbing the pics from.
file = ARGV

#you'll need to register an app with tumblr to get your oauth stuff.
client = Tumblr::Client.new({
  :consumer_key => '',
  :consumer_secret => '',
  :oauth_token => '',
  :oauth_token_secret => ''
 })

#this reads my text file (from the argument above)
image_id = IO.readlines("#{file[0]}")

#this loop iterates for every line of the file
image_id.collect! do |x|
    #this is to parse the URL so we can get data
    break_up = URI::parse(x)
	#this grabs the path (the part after the domain name)
	path = break_up.path
	#these two are for removing tumblr's /post/ and grabs the post id
	first_pass = path.gsub(/\/post\//, "")
	post_id = first_pass.gsub(/\/.*$/, "")
	#this is to grab the hostname of the blog.
	host = break_up.host
    
    #this is the api call. since photosets can only have 10 pics, that's the limit.
    all_data = client.posts("#{host}", :id => post_id, :type => "photo", :limit => 10)
    #gets the post data
    post_data = all_data.fetch("posts")
	#hashes that data
	post_hash = Hash[post_data[0]]
	#grabs the value for 'photos'
	photos = post_hash.fetch("photos")
 
    #Pics from a tumblr post come in many sizes, so this is actually its own hash and this loop iterates over that hash.
    photos.each do |i|
		#this gets the data for the highest resolution image
		original = i.fetch("original_size")
		#this grabs the image URL
		original_url = original.fetch("url")
		#this is to write the file (eg, download the image) to your current dir.
		File.open("#{post_id}" + ".jpg" || ".png", 'wb') do |f|
		    f.write open("#{original_url}").read
		end
	end
    
end