Graphics::ColorNames - defines RGB values for common color names

CWGraphics::ColorNames should work on Perl 5.6.0. It requires the following non-standard modules:

  Module::Load

Installation is pretty standard:

  perl Makefile.PL
  make
  make test
  make install

  use Graphics::ColorNames qw( hex2tuple tuple2hex );

  tie %NameTable, 'Graphics::ColorNames', 'X';

  my $rgbhex1 = $NameTable{'green'};    # returns '00ff00'
  my $rgbhex2 = tuple2hex( 0, 255, 0 ); # returns '00ff00'
  my @rgbtup  = hex2tuple( $rgbhex );   # returns (0, 255, 0)

  my $rgbhex3 = $NameTable{'#123abc'};  # returns '123abc'
  my $rgbhex4 = $NameTable{'123abc'};   # returns '123abc'

This module defines RGB values for common color names. The intention is to (1) provide a common module that authors can use with other modules to specify colors; and (2) free module authors from having to re-invent the wheel whenever they decide to give the users the option of specifying a color by name rather than RGB value.

For example,

  use Graphics::ColorNames 'hex2tuple';
  tie %COLORS, 'Graphics::ColorNames';

  use GD;

  $img = new GD::Image(100, 100);

  $bgColor = $img->colorAllocate( hex2tuple( $COLORS{'CadetBlue3'} ) );

Though a little 'bureaucratic', the meaning of this code is clearer: CW$bgColor (or background color) is 'CadetBlue3' (which is easier to for one to understand than CW0x7A, 0xC5, 0xCD). The variable is named for its function, not form (ie, CW$CadetBlue3) so that if the author later changes the background color, the variable name need not be changed.

As an added feature, a hexidecimal RGB value in the form of #RRGGBB or RRGGBB will return itself:

  my $rgbhex3 = $NameTable{'#123abc'};  # returns '123abc'

The standard interface (prior to version 0.40) is through a tied hash:

  tie %NAMETABLE, 'Graphics::ColorNames', @SCHEME

where CW%NAMETABLE is the tied hash and CW@SCHEME is a list of color schemes or the path to or open filehandle for a rgb.txt file.

Multiple schemes can be used:

  tie %COLORS, 'Graphics::ColorNames', qw(HTML Windows Netscape);

In this case, if the name is not a valid HTML color, the Windows name will be used; if it is not a valid Windows name, then the Netscape name will be used.

RGB values can be retrieved with a case-insensitive hash key:

  $rgb = $colors{'AliceBlue'};

The value returned is in the six-digit hexidecimal format used in HTML and CSS (without the initial '#'). To convert it to separate red, green, and blue values (between 0 and 255), use the hex2tuple function.

If you prefer, an object-oriented interface is available:

  $obj = Graphics::ColorNames->new('/etc/rgb.txt');

  $hex = $obj->hex('skyblue'); # returns "87ceeb"

  @rgb = $obj->rgb('skyblue'); # returns (0x87, 0xce, 0xeb)

The interface is similar to the Color::Rgb module:

new

  $obj = Graphics::ColorNames->new( @SCHEMES );

Creates the object, using the default color schemes. If none are specified, it uses the CWX scheme.

hex

  $hex = $obj->hex($name, $prefix);

Returns a 6-digit hexidecimal RGB code for the color. If an optional prefix is specified, it will prefix the code with that string. For example,

  $hex = $obj->hex('blue', '#'); # returns "#0000ff"

rgb

  @rgb = $obj->rgb($name);

  $rgb = $obj->rgb($name, $separator);

If called in a list context, returns a triplet. If called in a scalar context, returns a string separated by an optional separator (which defauls to a comma). For example,

  @rgb = $obj->rgb('blue');      # returns (0, 0, 255)

  $rgb = $obj->rgb('blue', ','); # returns "0,0,255"

These functions are not exported by default, so much be specified to be used:

  use Graphics::ColorNames qw( hex2tuple tuple2hex );

hex2tuple

  ($red, $green, $blue) = hex2tuple( $colors{'AliceBlue'});

tuple2hex

  $rgb = tuple2hex( $red, $green, $blue );

The following schemes are available by default:

X

About 750 color names used in X-Windows. This is the default naming scheme, since it provides the most names.

HTML

16 common color names defined in the HTML 4.0 specification. These names are also used with CSS and SVG.

Netscape

100 color names names associated Netscape 1.1 (I cannot determine whether they were once usable in Netscape or were arbitrary names for RGB values many of these names are not recognized by later versions of Netscape). This scheme may be deprecated in future versions, but available as a separate module.

Windows

16 commom color names used with Microsoft Windows and related products. These are actually the same colors as CWHTML, although with different names.

Rather than a color scheme, the path or open filehandle for a rgb.txt file may be specified.

Additional color schemes may be available on CPAN.

You can add naming scheme files by creating a Perl module is the name CWGraphics::ColorNames::SCHEMENAME which has a subroutine named CWNamesRgbTable that returns a hash of color names and RGB values.

The color names must be in all lower-case, and the RGB values must be 24-bit numbers containing the red, green, and blue values in most- significant to least- significant byte order.

An example naming schema is below:

  package Graphics::ColorNames::Metallic;

  sub NamesRgbTable() {
    use integer;
    return {
      copper => 0xb87333,
      gold   => 0xcd7f32,
      silver => 0xe6e8fa,
    };
  }

You would use the above schema as follows:

  tie %colors, 'Graphics::ColorNames', 'Metallic';

An example of an additional module is Steve Pomeroy's Graphics::ColorNames::Mozilla module.

Since version 1.03, CWNamesRgbTable may also return a code reference:

  package Graphics::ColorNames::Orange;

  sub NamesRgbTable() {
    return sub {
      my $name = shift;
      return 0xffa500;        
    };
  }

See Graphics::ColorNames::GrayScale for an example.

Note that extentions of the form Graphics::ColourNames::* are not supported.

Color::Rgb has a similar function to this module, but parses an rgb.txt file.

Graphics::ColorObject can convert between RGB and other color space types.

  R - Released
  d - Developer
  p - Perl-only
  h - Hybrid interface
  p - Standard Perl

See <http://cpan.uwinnipeg.ca/htdocs/faqs/dslip.html>

Robert Rothenberg <rrwo at cpan.org>

Alan D. Salewski <alans at cji.com> for feedback and the addition of CWtuple2hex.

Steve Pomeroy <xavier at cpan.org> for pointing out invalid color definitions in X color space.

<chemboy at perlmonk.org> who pointed out a mispelling of fuchsia in the HTML color space <http://rt.cpan.org/Ticket/Display.html?id=1704>.

<magnus at mbox604.swipnet.se> who pointed out mispellings and naming inconsistencies.

Feedback is always welcome. Please use the CPAN Request Tracker at <http://rt.cpan.org> to submit bug reports.

If you create additional color schemes, please make them available separately in CPAN rather than submit them to me for inclusion into this module.

Copyright (c) 2001-2005 Robert Rothenberg. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.