Rake task to create thumbnails of static images

covers.rake

require 'mini_magick'

namespace :covers do
  def covers_path
    Rails.root.join('app', 'assets', 'images', 'covers')
  end

  def files_inside_covers_path
    Dir.glob(covers_path.to_s << '/**/*').select { |path| File.file?(path) }
  end

  def covers
    files_inside_covers_path.reject { |path| path.include?('_thumbnail') }
  end

  def thumbnails
    files_inside_covers_path.select { |path| path.include?('_thumbnail') }
  end

  desc 'Generate thumbnails versions of existing covers'
  task :create_thumbnails do
    covers.each do |cover_path|
      destination_path = cover_path.gsub('.jpg', '_thumbnail.jpg')

      MiniMagick::Image.open(cover_path).tap do |cover|
        cover.resize('32%')
        cover.write(destination_path)
      end
    end
  end

  desc 'Delete thumbnails versions of existing covers'
  task :destroy_thumbnails do
    thumbnails.each do |thumbnail_path|
      File.delete(thumbnail_path)
    end
  end
end