Acme::Colour - additive and subtractive human-readable colours


  # light
  $c = Acme::Colour->new("black");
  $colour = $c->colour; # black
  $c->add("red");   # $c->colour now red
  $c->add("green"); # $c->colour now yellow

  # pigment
  $c = Acme::Colour->new("white");
  $c->mix("cyan");    # $c->colour now cyan
  $c->mix("magenta"); # $c->colour now blue


The Acme::Colour module mixes colours with human-readable names.

There are two types of colour mixing: the mixing of lights and the mixing of pigments. If one take two differently coloured beams of light and projects them on to a screen, the mixing of these lights occurs according to the principle of additive colour mixing. If one mixes two differently coloured paints they mix according to the principle of subtractive colour mixing.



The new() method creates a new colour. It takes an optional argument which is the initial colour used:

  $c = Acme::Colour->new("black");


The colour() method returns the current colour. Note that stringification of the colour object magically returns the colour too:

  $colour = $c->colour; # black
  print "The colour is $c!\n";


The add() method performs additive mixing on the colour. It takes in the colour to add in:



The mix() method performs subtractive mixing on the colour. It takes in the colour to mix in:



The default() method returns the default colour, white. You may override this in a subclass.

  $c = Acme::Colour->new(); # white by default


There is an alternative interface to this module which overloads string quoting. This is very cute, but is not recommended in production code. Strings containing colour names magically get converted into Acme::Colour objects and additive and subtractive mixing is performed on these "strings" using "+" and "-":

  use Acme::Colour constants => 1; # note special invocation

  my $red = "red";            # now an Acme::Colour object
  my $green = "green";        # likewise
  my $yellow = $red + $green; # add()s the two colours

  my $cyan = "cyan";           # now an Acme::Colour object
  my $magenta = "magenta";     # likewise
  my $blue = $cyan - $magenta; # mix()es the two colours


A good explanation of colour and colour mixing is available at:

This module throws an exception upon unknown colours.

No, "colour" is not a typo.


Leon Brocard <>


Copyright (C) 2002-3, Leon Brocard

This module is free software; you can redistribute it or modify it under the same terms as Perl itself.