Preview terminal background and foreground

terminal_color_preview.rb

raise 'COLORTERM required' unless ENV['COLORTERM']

# Color table from https://en.wikipedia.org/wiki/ANSI_escape_code#3-bit_and_4-bit
env_names = %w[VGA WinXP PowerShell6 VSCode Win10 Terminal.app PuTTY mIRC xterm Ubuntu Eclipse]
env_colors = <<COLORS.lines.map{|l|l.split(' ').map{_1.scan(/\d+/).join(';')}}.transpose
0,0,0 0,0,0 0,0,0 12,12,12 0,0,0 0,0,0 0,0,0 0,0,0 1,1,1 0,0,0
170,0,0 128,0,0 205,49,49 197,15,31 153,0,0 187,0,0 127,0,0 205,0,0 222,56,43 205,0,0
0,170,0 0,128,0 13,188,121 19,161,14 0,166,0 0,187,0 0,147,0 0,205,0 57,181,74 0,205,0
170,85,0 128,128,0 229,229,16 193,156,0 153,153,0 187,187,0 252,127,0 205,205,0 255,199,6 205,205,0
0,0,170 0,0,128 36,114,200 0,55,218 0,0,178 0,0,187 0,0,127 0,0,238 0,111,184 0,0,238
170,0,170 128,0,128 188,63,188 136,23,152 178,0,178 187,0,187 156,0,156 205,0,205 118,38,113 205,0,205
0,170,170 0,128,128 17,168,205 58,150,221 0,166,178 0,187,187 0,147,147 0,205,205 44,181,233 0,205,205
170,170,170 192,192,192 229,229,229 204,204,204 191,191,191 187,187,187 210,210,210 229,229,229 204,204,204 229,229,229
85,85,85 128,128,128 102,102,102 118,118,118 102,102,102 85,85,85 127,127,127 127,127,127 128,128,128 0,0,0
255,85,85 255,0,0 241,76,76 231,72,86 229,0,0 255,85,85 255,0,0 255,0,0 255,0,0 255,0,0
85,255,85 0,255,0 35,209,139 22,198,12 0,217,0 85,255,85 0,252,0 0,255,0 0,255,0 0,255,0
255,255,85 255,255,0 245,245,67 249,241,165 230,230,0 255,255,85 255,255,0 255,255,0 255,255,0 255,255,0
85,85,255 0,0,255 59,142,234 59,120,255 0,0,255 85,85,255 0,0,252 92,92,255 0,0,255 92,92,255
255,85,255 255,0,255 214,112,214 180,0,158 229,0,229 255,85,255 255,0,255 255,0,255 255,0,255 255,0,255
85,255,255 0,255,255 41,184,219 97,214,214 0,229,229 85,255,255 0,255,255 0,255,255 0,255,255 0,255,255
255,255,255 255,255,255 229,229,229 242,242,242 229,229,229 255,255,255 255,255,255 255,255,255 255,255,255 255,255,255
COLORS

def color_name(val)
  return 'gray' if val == 8
  "#{val>=8 ? 'bright_' : ''}#{%w[black red green yellow blue magenta cyan white][val%8]}"
end
black, red, green, yellow, blue, magenta, cyan, white, bright = *0..8
gray = bright | black
your_env = ARGV[0]

[[cyan, white], [cyan, black], [black, white], [white, black], [gray, white], [gray, black], [magenta, black], [magenta, white]].each do |bg, fg|
  puts "#{color_name(bg)} - #{color_name(fg)}"
  msg = "Your env(#{your_env}) #{[*'a'..'z'].join}"[0, 20]
  puts "\e[#{[40, 100][bg / 8] + bg % 8};#{[30, 90][fg / 8] + fg % 8}m#{msg}\e[m" if your_env
  env_colors.zip(env_names).each do |colors, name|
    msg = "#{name} #{[*'a'..'z'].join}"[0, 20]
    puts "\e[48;2;#{colors[bg]};38;2;#{colors[fg]}m#{msg}\e[m"
  end
  puts
end