LunarLogic/gauguin

Retrieves palette of main colors, merging similar colors using Lab color space.

Why not just use RMagick?

How many colors do you recognize on the image below?

Many people would say 2, but actually there are 1942.

It's because of the fact that to make image more smooth, borders of the figure are not pure black but consist of many gray scale colors.

It's common that images includes very similar colors, so when you want to get useful color palette, you would need to process color histogram you get from RMagick yourself.

This gem was created to do this for you.

Sample app

Sample application available here: http://gauguin.lunarlogic.io

Requirements

Gem depends on RMagick which requires ImageMagick to be installed.

Ubuntu

$ sudo apt-get install imagemagick

OSX

$ brew install imagemagick

Installation

Add this line to your application's Gemfile:

gem 'gauguin'

And then execute:

$ bundle

Or install it yourself as:

$ gem install gauguin

Usage

Palette

palette = Gauguin::Painting.new("path/to/image.png").palette

Result for image above would be:

  {
    rgb(204, 204, 204)[0.5900935269505287] => [
      rgb(77, 77, 77)[7.383706620723603e-05],
      rgb(85, 85, 85)[0.00012306177701206005],
      # ...
      rgb(219, 220, 219)[1.2306177701206005e-05],
      rgb(220, 220, 220)[7.383706620723603e-05]
    ],
    rgb(0, 0, 0)[0.40990647304947003] => [
      rgb(0, 0, 0)[0.40990647304947003],
      rgb(1, 1, 1)[0.007912872261875462],
      # ...
      rgb(64, 64, 64)[6.153088850603002e-05],
      rgb(66, 66, 66)[6.153088850603002e-05]
    ]
  }

Where keys are instances of Gauguin::Color class and values are array of instances of Gauguin::Color class.

Recolor

There is also recolor feature - you can pass original image and the calculated palette and return new image, colored only with the main colours from the palette.

painting.recolor(palette, 'path/where/recolored/file/will/be/placed')

Custom configuration

There are 4 parameters that you can configure:

• max_colors_count (default value is 10) - maximum number of colors that a palette will include
• colors_limit (default value is 10000) - maximum number of colors that will be considered while calculating a palette - if image has too many colors it is not efficient to calculate grouping for all of them, so only colors_limit of colors of the largest percentage are used
• min_percentage_sum (default value is 0.981) - parameter used while calculating which colors should be ignored. Colors are sorted by percentage in descending order, then colors which percentages sums to min_percentage_sum are taken into consideration
• color_similarity_threshold (default value is 25) - maximum distance in Lab color space to consider two colors as the same while grouping

To configure any of above options you can use configuration block. For example changing max_colors_count would look like this:

Gauguin.configuration do |config|
  config.max_colors_count = 7
end

Contributing

1. Fork it ( https://github.com/LunarLogic/gauguin/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request