Extract dominant colours from an image in Ruby using MiniMagick

extract_dominant_colors.rb

  def self.extract_dominant_colors(image_path, quantity=5, threshold=0.01)
    image = MiniMagick::Image.open(image_path)

    # Get image histogram
    result = image.run_command('convert', image_path, '-format', '%c', '-colors', quantity, '-depth', 8, 'histogram:info:')
    
    # Extract colors and frequencies from result
    frequencies = result.scan(/([0-9]+)\:/).flatten.map { |m| m.to_f }
    hex_values = result.scan(/(\#[0-9ABCDEF]{6,8})/).flatten
    total_frequencies = frequencies.reduce(:+).to_f

    # Create frequency/color pairs [frequency, hex],
    # sort by frequency,
    # ignore fully transparent colours
    # select items over frequency threshold (1% by default),
    # extract hex values,
    # return desired quantity
    frequencies
      .map.with_index { |f, i| [f / total_frequencies, hex_values[i]] }
      .sort           { |r| r[0] }
      .reject         { |r| r[1].end_with?('FF') }
      .select         { |r| r[0] > threshold }
      .map            { |r| r[1][0..6] }
      .slice(0, quantity)
  end

Shouldn't it reject values ending in 00 instead of FF?