Usage:

pic_online = ShackMirror.new(local_path_of_pic)
pic_online.url # => returns direct link on Imageshack.

NOTE: if you give it a path beginning with http, then it will transload the image directly to Imageshack. Cool!

require 'rubygems'
require 'hpricot'
require 'net/http'
require 'uri'
require 'cgi'
require 'mime/types'

class ShackMirror

SHACK_ID = "REPLACE WITH YOUR OWN IMAGESHACK ID"
USER_AGENT = "Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en) AppleWebKit/419 (KHTML, like Gecko) Safari/419.3"
BOUNDARY = '----------PuSHerInDaBUSH_$'

attr_reader :url

def initialize(img)
    raise NonImageTypeError, 'Expected image file.' unless img =~ /jpe?g|png|gif|bmp|tif|tiff|swf$/
    @img = img
    @url, @hosturi, @res = "","",""
    @header, @params = {}, {}
    @header['Cookie'] = "myimages=#{SHACK_ID}"
    @header['User-Agent'] = USER_AGENT
    @params['uploadtype'] = 'on'  
    @params['brand'] = ''
    @params['refer'] = ''
    @params['MAX_FILE_SIZE'] = '13145728'
    @params['optimage'] = '0'
    @params['rembar'] = '1'
    transfer
    getdirect
end

protected

def prepare_multipart ( params )
    fp = []
    params.each do |k,v|
    if v.respond_to?(:read)
      fp.push(FileParam.new(k,v.path,v.read))
      else fp.push(Param.new(k,v)) 
    end
  end
    query = fp.collect {|p| "--" + BOUNDARY + "\r\n" + p.to_multipart }.join("") + "--" + BOUNDARY + "--"
    return query
end

def prepFile(path_to_file)

  file = File.new(path_to_file)

  @header['Content-Type'] = "multipart/form-data, boundary=" + BOUNDARY + " "

  @params['url'] = 'paste image url here'
  @params['fileupload'] = file
  
  $query = prepare_multipart(@params)
  file.close

end

def locate(path)
  path !~ /^http/ ? "local" : "remote"
end

def upload( query, headers={} )
  Net::HTTP.start(@hosturi.host) do | http |
    http.post(@hosturi.path, query, headers);
  end
end

def transload(url)

  @header['Content-Type'] = 'form-data'

  @params['url'] = url
  @params['fileupload'] = ''
  
  postreq = Net::HTTP::Post.new(@hosturi.path, @header)
  postreq.set_form_data(@params)

  return Net::HTTP.new(@hosturi.host, @hosturi.port).start { |http| http.request(postreq) }

end

def transfer

case locate(@img)
  when "local"
    @hosturi = URI.parse('http://load.imageshack.us/index.php')
    prepFile(@img)
    @res = upload($query,@header)
  when "remote"
    @hosturi = URI.parse('http://imageshack.us/transload.php')
    @res = transload(@img)
end

end

def getdirect
  doc = Hpricot(@res.body)
  @url = (doc/"//input").last['value']
end

end

class Param

  attr_accessor :k, :v

  def initialize( k, v )
    @k = k
    @v = v
  end
  
  def to_multipart
    return "Content-Disposition: form-data; name=\"#{CGI::escape(k)}\"\r\n\r\n#{v}\r\n"
  end

end

class FileParam

  attr_accessor :k, :filename, :content

  def initialize( k, filename, content )
    @k = k
    @filename = filename
    @content = content
  end
  
  def to_multipart
    return "Content-Disposition: form-data; name=\"#{CGI::escape(k)}\"; filename=\"#{filename}\"\r\n" +
    "Content-Type: #{MIME::Types.type_for(@filename)}\r\n\r\n" + content + "\r\n"
  end

end