man Graphics::ColorNames (3): defines RGB values for common color names

SYNOPSIS

use Graphics::ColorNames 2.10;
$po = new Graphics::ColorNames(qw( X ));
$rgb = $po->hex('green'); # returns '00ff00'
$rgb = $po->hex('green', '0x'); # returns '0x00ff00'
$rgb = $po->hex('green', '#'); # returns '#00ff00'
$rgb = $po->rgb('green'); # returns '0,255,0'
@rgb = $po->rgb('green'); # returns (0, 255, 0)
$rgb = $po->green; # same as $po->hex('green');
tie %ph, 'Graphics::ColorNames', (qw( X ));
$rgb = $ph{green}; # same as $po->hex('green');

DESCRIPTION

This module provides a common interface for obtaining the RGB values of colors by standard names. The intention is to (1) provide a common module that authors can use with other modules to specify colors by name; 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 2.10;
  use GD;
  $pal = new Graphics::ColorNames;
  $img = new GD::Image(100, 100);
  $bgColor = $img->colorAllocate( $pal->rgb('CadetBlue3') );

Although this is a little ``bureaucratic'', the meaning of this code is clear: $bgColor (or background color) is 'CadetBlue3' (which is easier to for one to understand than "0x7A, 0xC5, 0xCD"). The variable is named for its function, not form (ie, $CadetBlue3) so that if the author later changes the background color, the variable name need not be changed.

You can also define ``Custom Color Schemes'' for specialised palettes for websites or institutional publications:

  $color = $pal->hex('MenuBackground');

As an added feature, a hexidecimal RGB value in the form of #RRGGBB, 0xRRGGBB or RRGGBB will return itself:

  $color = $pal->hex('#123abc');         # returns '123abc'

Tied Interface

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

  tie %pal, 'Graphics::ColorNames', @schemes;

where %pal is the tied hash and @schemes is a list of color schemes.

A valid color scheme may be the name of a color scheme (such as "X" or a full module name such as "Graphics::ColorNames::X"), a reference to a color scheme hash or subroutine, or to the path or open filehandle for a rgb.txt file.

As of version 2.1002, one can also use Color::Library dictionaries:

  tie %pal, 'Graphics::ColorNames', qw(Color::Library::Dictionary::HTML);

This is an experimental feature which may change in later versions (see ``SEE ALSO'' for a discussion of the differences between modules).

Multiple schemes can be used:

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

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

One can load all available schemes in the Graphics::ColorNames namespace (as of version 2.0):

  use Graphics::ColorNames 2.0, 'all_schemes';
  tie %NameTable, 'Graphics::ColorNames', all_schemes();

When multiple color schemes define the same name, then the earlier one listed has priority (however, hash-based color schemes always have priority over code-based color schemes).

When no color scheme is specified, the X-Windows scheme is assumed.

Color names are case insensitive, and spaces or punctuation are ignored. So ``Alice Blue'' returns the same value as ``aliceblue'', ``ALICE-BLUE'' and ``a*lICEbl-ue''. (If you are using color names based on user input, you may want to add additional validation of the color names.)

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.

Object-Oriented Interface

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

  use Graphics::ColorNames 0.40;
  $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 "X" scheme.

load_scheme

  $obj->load_scheme( $scheme );

Loads a scheme dynamically. The scheme may be any hash or code reference.

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"

Since version 2.10_02, the interface will assume method names are color names and return the hex value,

  $obj->black eq $obj->hex("black")

Method names are case-insensitive, and underscores are ignored.

Utility Functions

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

  use Graphics::ColorNames qw( all_schemes hex2tuple tuple2hex );

all_schemes

  @schemes = all_schemes();

Returns a list of all available color schemes installed on the machine in the Graphics::ColorNames namespace.

The order has no significance.

hex2tuple

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

tuple2hex

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

Color Schemes

The following schemes are available by default:

X: About 750 color names used in X-Windows (although about 90+ of them are duplicate names with spaces).
HTML: 16 common color names defined in the HTML 4.0 specification. These names are also used with older CSS and SVG specifications. (You may want to see Graphics::ColorNames::SVG for a complete list.)
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 the ``HTML'' scheme, 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.

Custom Color Schemes

You can add naming scheme files by creating a Perl module is the name "Graphics::ColorNames::SCHEMENAME" which has a subroutine named "NamesRgbTable" that returns a hash of color names and RGB values. (Schemes with a different base namespace will require the fill namespace to be given.)

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';

The behavior of specifying multiple keys with the same name is undefined as to which one takes precedence.

As of version 2.10, case, spaces and punctuation are ignored in color names. So a name like ``Willy's Favorite Shade-of-Blue'' is treated the same as ``willysfavoroteshadeofblue''. (If your scheme does not include duplicate entrieswith spaces and punctuation, then the minimum version of Graphics::ColorNames should be 2.10 in your requirements.)

An example of an additional module is the Graphics::ColorNames::Mozilla module by Steve Pomeroy.

Since version 1.03, "NamesRgbTable" 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.

Graphics::ColourNames

The alias ``Graphics::ColourNames'' (British spelling) is no longer available as of version 2.01.

It seems absurd to maintain it when all the modules does is provide an alternative spelling for the module name without doing anything about the component colors of each scheme, and when most other modules (and non-Perl software) does not bother with such things.

AUTHOR

Robert Rothenberg <rrwo at cpan.org>

Acknowledgements

Alan D. Salewski <alans at cji.com> for feedback and the addition of "tuple2hex".

Steve Pomeroy <xavier at cpan.org>, ``chemboy'' <chemboy at perlmonk.org> and ``magnus'' <magnus at mbox604.swipnet.se> who pointed out issues with various color schemes.

Suggestions and Bug Reporting

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

There is a Sourceforge project for this package at <http://sourceforge.net/projects/colornames/>.

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