#!/usr/bin/env ruby 
require 'RMagick'
require 'progressbar'
require 'base64'

class DupeMagick

  attr_accessor :source_vector, :target_vector, :source_cube, :target_cube, :distance

  def compare_images(source, target, params)
    source_image = process_image(source, params)
    target_image = process_image(target, params)
    @source_vector = create_vector_from_image(source_image)
    @source_cube = create_cube_from_vector(@source_vector)
    @target_vector = create_vector_from_image(target_image)
    @target_cube = create_cube_from_vector(@target_vector)
    @distance = calculate_euclidian_distance(@source_cube, @target_cube)
    puts "Images are " + euclidian_plain_language(@distance) + ", score: " + @distance.to_i.to_s
    @distance.to_i
  end

  def find_duplicates(source_file, target_path)
    source_image = process_image(source_file, {:geometry => '8x8!'})
    @source_vector = create_vector_from_image(source_image)
    @source_cube = create_cube_from_vector(@source_vector)
    files = files_in_directory(target_path)
    files.each do |target|
      target_image = process_image(target, {:geometry => '8x8!'})
      @target_vector = create_vector_from_image(target_image)
      @target_cube = create_cube_from_vector(@target_vector)
      @distance = calculate_euclidian_distance(@source_cube, @target_cube)
      puts "Images are " + euclidian_plain_language(@distance) + ", score: " + @distance.to_i.to_s
    end
  end

  def serialize(obj)
    # for storing image data as a blob in mysql etc
    Base64.encode64(Marshal.dump(obj))
  end

  def deserialize(obj)
    # for retrieving image data from a blob in mysql etc
    Base64.decode64(Marshal.load(obj))
  end

  private

  def read_image(file)
    Magick::Image.read(file).first
  end

  def files_in_directory(path)
    Dir[path]
  end

  def do_make_progress_bar (title, total)
    ProgressBar.new(title, total)
  end

  def process_image(image, params)
    # read image
    image = read_image(image)

    # normalize image
    image = image.normalize
   
    # strip off 10% border 
    image = image.excerpt((image.columns * 10/100).to_i, (image.rows * 10/100).to_i,
      (image.columns * 90/100).to_i, (image.rows * 90/100).to_i)
    
    # optionally quantize image to 32 colours
    image = image.quantize(32, Magick::RGBColorspace) if params[:quantize]
    
    # optionally blur image  
    image = image.gaussian_blur(0.0, params[:blur_radius]) if params[:blur]
    
    # change geometry of image
    image = image.change_geometry(params[:geometry]) { |cols, rows, img| img.resize!(cols, rows)}

    image
  end

  def create_vector_from_image(image)
    image.export_pixels(0, 0, image.columns, image.rows, "RGB")
  end

  def create_cube_from_vector(vector)
    # create cube 8x8x8 for each channel
    cube = Hash.new
    cube[:r]  = Hash.new 0
    cube[:g]  = Hash.new 0
    cube[:b]  = Hash.new 0
    array_mod(vector, 3, 0).each { |r| cube[:r][which_bin(r)] += 1 } 
    array_mod(vector, 3, 1).each { |g| cube[:g][which_bin(g)] += 1 } 
    array_mod(vector, 3, 2).each { |b| cube[:b][which_bin(b)] += 1 }
    cube
  end

  def which_bin(channel)
    case channel
      when 0..8191      then 1
      when 8192..16383  then 2
      when 16384..24575 then 3
      when 24576..32767 then 4
      when 32768..40959 then 5
      when 40960..49151 then 6
      when 49152..57343 then 7
      when 57344..65535 then 8
    end
  end

  def array_mod(arr, mod, offset = 0)
    arr.shift(offset)
    out_arr = []
    arr.each_with_index do |val, idx|
      out_arr << val if idx % mod == 0
    end
    out_arr
  end
  
  def calculate_euclidian_distance(source_cube, target_cube)
    sum = Hash.new 0
    1.upto(8) do |r|
      1.upto(8) do |g|
        1.upto(8) do |b|
          sum[:r] += (target_cube[:r][r] - source_cube[:r][r])**2 
          sum[:g] += (target_cube[:g][g] - source_cube[:g][g])**2 
          sum[:b] += (target_cube[:b][b] - source_cube[:b][b])**2 
        end
      end
    end
    Math.sqrt(sum[:r] + sum[:g] + sum[:b])
  end

  def euclidian_plain_language(distance)
    case distance
      when 0       then "identical"
      when 1..50   then "similar"
      when 51..150 then "possibly similar"
      else "different" 
    end
  end

end