Color search for Rails
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Kaleidoscope is color search for Rails using Active Record and Paperclip.

Kaleidoscope uses k-means clustering to segment a database of images into color bins for quick searching. You can use this for color search in a photo-sharing site or even for a retail application (look at all the purple purses!).

Heres's how it works:

  1. Pick a Paperclip model that has image attachments, for example Photo.

  2. Kaleidoscope runs histograms on Photo's images and converts their top n most frequent colors into Lab* color space for an approximate representation of human vision.

  3. Colors are then matched to a user-defined set of colors using Euclidean distance, i.e. a "bin". We have a default set of 28 web-safe colors, but you can choose any array of RGB values.

  4. The gem will store hexadecimal values of the image's original color and the matched color, along with the frequency of that color within the image (for sorting based on frequency) and the Euclidean distance (for sorting by tolerance).

  5. You can simply call Photo.all.with_color('#993399') (like in the example below) and order by frequency and Euclidean distance. You can also use @photo.colors for display.

  6. New records are automagically segmented into bins for you.

Since Lab* relies so heavily on lightness, matches for white, black, and grey will all be quite poor compared to other color types.

Here's an example of what Kaleidoscope can do:

Kaleidoscope Example



Currently Kaleidoscope requires you to have Paperclip already run on the model you want indexed for color search.

In the future, it would be nice if Paperclip were not a requirement and Kaleidoscope could work with, say, CarrierWave.

Image Processor

ImageMagick must be installed and Kaleidoscope must have access to it via RMagick. To ensure that it does, on your command line, run which convert (one of the ImageMagick utilities). This will give you the path where that utility is installed. For example, it might return /usr/local/bin/convert/.

If you're on Mac OS X, you'll want to run the following with Homebrew:

brew install imagemagick


Add this line to your application's Gemfile:

gem 'kaleidoscope'

And then execute:

$ bundle

Or install it yourself as:

$ gem install kaleidoscope

After installing, you must run:

$ rails generate kaleidoscope:install

This will generate the file config/initializers/kaleidoscope.rb where you can customize your install.

Quick Start

Generate your migration by specifying the Paperclip model, e.g. Photo:

rails generate kaleidoscope photo

This will generate the model PhotoColor.

Alternatively, in your models:

class Photo < ActiveRecord::Base
  has_many :photo_colors

class PhotoColor < ActiveRecord::Base
  belongs_to :photo

  attr_accessible :photo_id, :distance, :frequency, :original_color, :reference_color

And in your migrations:

class AddPhotoColors < ActiveRecord::Migration
  def change
    create_table :photo_colors do |t|
      t.integer :photo_id
      t.string :original_color
      t.string :reference_color
      t.float :frequency
      t.integer :distance


    add_index :photo_colors, :photo_id
    add_index :photo_colors, :original_color
    add_index :photo_colors, :reference_color
    add_index :photo_colors, :frequency
    add_index :photo_colors, :distance

In your controller:

def index
  @photos = Photo.all.with_color(params[:color])

To refresh the color database:

rake kaleidosocope:refresh


The basics of Kaleidoscope are simple: declare that your model has colors with the has_colors method.

Kaleidoscope creates a related model <model>_color that wraps up to four attributes and gives them a friendly front end. These attributes are:

  • original_color - the original color found in the image
  • reference_color - a matched color based on user-defined reference points
  • frequency - the percentage that color appears in the image
  • distance - Euclidean distance of original color from reference color

Kaleidoscope will create a record for each color you extract from your images.


To run the RSpec tests, simply:

rake spec


Please submit pull requests! I'd love to feature you as a contributor. Here's a guide:

  1. Fork the repo.
  2. Run the tests. We only take pull requests with passing tests.
  3. Add a test for your change. Only refactoring and documentation changes require no new tests. If you are adding functionality or fixing a bug, we need a test.
  4. Make the test pass.
  5. Push to your fork and submit a pull request.

We'll review your changes, comment, and then accept or throw it back to you for improvement.


  • Two spaces, no tabs.
  • No trailing whitespace.
  • Prefer &&/II over and/or.
  • a = b and not a=b
  • Follow conventions you see used in the source already.


  1. Enable Kaleidoscope to work without requiring Paperclip. Ideally, any database of images should be searchable and we don't want to be tied down to one specific gem.


Huge shoutout to Jamis Buck for releasing the Kaleidoscope name on RubyGems. Y'all should consider him honorary grandpa of this project.