module BBS::Art::Colors

The class methods of an Art for its colours: a palette entry as a Color (Art.color), the xterm 256-colour index of an RGB colour (Art.ansi256) and back (Art.rgb256), and the SGR of a cell (Art.sgr).

Constants

SYSTEM_RGB: The default colours of xterm’s first sixteen indexes.

Public Instance Methods

ansi256 (rgb)

Source

# File lib/bbs/art/colors.rb, line 29
def ansi256(rgb) = (16..255).min_by { |i| rgb256(i).zip(rgb).sum { |a, b| (a - b)**2 } }

The xterm 256-colour index nearest to rgb, [red, green, blue], from the colour cube and the grey ramp (16-255: the first sixteen differ from terminal to terminal).

color (value)

Source

# File lib/bbs/art/colors.rb, line 11
def color(value)
  case value
  when Integer
    raise ArgumentError, "a 256-colour index is 0-255, not #{value}" unless value.between?(0, 255)

    Color.new(Petscii::Canvas.nearest(rgb256(value)), value)
  when /\A#\h{6}\z/
    rgb = value[1..].scan(/../).map(&:hex)
    Color.new(Petscii::Canvas.nearest(rgb), ansi256(rgb))
  else
    c64 = Petscii::Canvas.color(value)
    Color.new(c64, ansi256(Petscii::Canvas::RGB[c64]))
  end
end

The Color of value, a palette entry: a C64 colour name, a 256-colour index or #rrggbb. Raises ArgumentError for anything else.

rgb256 (index)

Source

# File lib/bbs/art/colors.rb, line 33
def rgb256(index)
  return SYSTEM_RGB[index] if index < 16
  return [8 + ((index - 232) * 10)] * 3 if index >= 232

  i = index - 16
  [CUBE[i / 36], CUBE[(i / 6) % 6], CUBE[i % 6]]
end

The [red, green, blue] of xterm 256-colour index index (the first sixteen as xterm’s defaults).

sgr (cell)

Source

# File lib/bbs/art/colors.rb, line 48
def sgr(cell)
  parts = ['0']
  parts << "38;5;#{cell.fg.ansi}" if cell.fg
  parts << "48;5;#{cell.bg.ansi}" if cell.bg
  parts << '7' if cell.rvs
  "\e[#{parts.join(';')}m"
end

The SGR sequence of cell: a reset, then its 256-colour foreground and background and reverse video.