Vimfix is a ruby script made to help port vim color schemes to xterm-256color terminals

vimfix.rb

#!/usr/bin/ruby

class Array
  # classic implementation using the left fold
  # from StackOverflow
  def min_index
    champ = self.each_with_index.inject([1000, 0]) do |c, (v, i)|
      cv = c[0]; ci = c[1];
      if v <= cv
        [v, i]
      else
        [cv, ci]
      end
    end
    
    champ[1]
  end
end

class Rgb
  attr_accessor :r, :g, :b

  def initialize(r, g, b)
    raise "Color components must be subtractible, 'r' is #{r.class}" unless r.respond_to? :-
    raise "Color components must be subtractible, 'g' is #{g.class}" unless g.respond_to? :-
    raise "Color components must be subtractible, 'b' is #{b.class}" unless b.respond_to? :-
    @r = r; @g = g; @b = b
  end

  def self.from_s(string)
    rgb = Rgb.from_hash(string)
    return rgb unless rgb.nil?

    rgb = Rgb.from_name(string)
    return rgb # even if nil
  end
    
  def self.from_hash(hash)
    hash.match(/#([[:xdigit:]]{2})([[:xdigit:]]{2})([[:xdigit:]]{2})/) do |match|
      return Rgb.new(match[1].hex, match[2].hex, match[3].hex)
    end

    nil
  end

  def self.from_name(name)
    @@name2rgb.has_key?(name.downcase) ? @@name2rgb[name.downcase] : nil
  end

  def -(rgb)
    raise "Must subtract an Rgb from an Rgb" unless rgb.instance_of? Rgb

    Rgb.new(self.r - rgb.r, self.g - rgb.g, self.b - rgb.b)
  end

  # source: StackOverflow
  # uses absolute values so that it could be used
  # as a norm (not Euclidean, though)
  def luma
    0.2126 * @r.abs + 0.7152 * @g.abs + 0.0722 * @b.abs
  end

  def to_256
    # we add 16 to account for not using the standard colors
    @@cterm2rgb.map { |x| (x - self).luma }.min_index + 16
  end

  #############################################
  # initialize the conversion table
  #############################################

  # initialize the array for the cterm => rgb conversion
  @@cterm2rgb = Array.new
=begin
  # removed to prevent 16 (remappable) colors from creeping in
  @@cterm2rgb = [Rgb.from_hash('#000000'),
                 Rgb.from_hash('#800000'),
                 Rgb.from_hash('#008000'),
                 Rgb.from_hash('#808000'),
                 Rgb.from_hash('#000080'),
                 Rgb.from_hash('#800080'),
                 Rgb.from_hash('#008080'),
                 Rgb.from_hash('#c0c0c0'),

                 Rgb.from_hash('#808080'),
                 Rgb.from_hash('#ff0000'),
                 Rgb.from_hash('#00ff00'),
                 Rgb.from_hash('#ffff00'),
                 Rgb.from_hash('#0000ff'),
                 Rgb.from_hash('#ff00ff'),
                 Rgb.from_hash('#00ffff'),
                 Rgb.from_hash('#ffffff')]
=end
  intensities = [0x00, 0x5f, 0x87, 0xaf, 0xdf, 0xff]
  intensities.each do |r|
    intensities.each do |g|
      intensities.each do |b|
        @@cterm2rgb << Rgb.new(r, g, b)
      end
    end
  end

  0.upto(23).each do |shade|
    i = 0x08 + 10 * shade
    @@cterm2rgb << Rgb.new(i, i, i)
  end

  # test output
  # @@cterm2rgb.each_with_index { |x, i| puts i.to_s + ' ' + x.to_256.to_s }
  
  #############################################
  # initialize the X11 color names table
  #############################################

  @@name2rgb = Hash.new
  File.open("/etc/X11/rgb.txt") do |file|
    file.lines do |line|
      # goes like r g b name
      line.match(/\s*(\d+)\s*(\d+)\s*(\d+)\s*(\S+)/) do |match|
        @@name2rgb[match[4].downcase] = Rgb.new(match[1].to_i, match[2].to_i, match[3].to_i)
      end
    end
  end
end

# Reads vim color scheme from stdin, translates all rgb colors into their
# 256color counterparts, and outputs the fixed strings containing these numbers
# to stdout while also changing 'gui' => 'cterm'.
# 
# Use it to quickly obtain cterm colors and them splice them back into the
# color scheme manually

$stdin.lines do |line|
  result = line.gsub(/gui(\w*)=(#[[:digit:]]{6}|\S+)/) do |match|
    parsed = Rgb.from_s($2)
    out = parsed.nil? ? $2 : parsed.to_256

    "cterm#{$1}=#{out}"
  end

  # print only the lines that were changed
  puts result.chomp unless result == line
end