download_ny_photos_2.rb

# Adding RMagick to combine images

require 'open-uri'
require 'uri'
require 'rmagick'

class PhotoDownloader
  RESOURCE = 'http://access.nypl.org/image.php/'

  def initialize(id, zoom, dimension)
    @id = id
    @zoom = zoom
    @width, @height = dimension
  end

  def save
    0.upto(@height-1) do |height|
      0.upto(@width-1) do |width|
        download(form_url(height, width), "#{@id}_#{height}_#{width}.png")
      end
    end
  end

  def combine
    @tiles ||= save
    @image_list = Magick::ImageList.new

    verticals = @tiles.each_with_index.map do |tiles, n|
      image_list = Magick::ImageList.new
      combine = "combine-#{n}.png"

      tiles.each do |tile|
        image_list.push(Magick::Image.from_blob(tile).first)
      end

      image_list.append(true)
    end

    verticals.each do |combine|
      @image_list.push(combine)
    end

    @image_list.append(false).write("#{@id}.png")
  end

  private

  def form_url(x,y)
    URI.join(RESOURCE, "#{@id}/", fetch_tile(x,y))
  end

  def fetch_tile(x = 0, y = 0)
    "tiles/0/#{@zoom}/#{x}_#{y}.png"
  end
end