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Graph/colour.pm  view on Meta::CPAN

    @{$rgb_ref};
}

=head2 _hue( I<R,G,B> )

Returns the hue of the colour with the specified RGB values.
Exported with the :colours tag.

=head2 _luminance( I<R,G,B> )

Returns the luminance of the colour with the specified RGB values.
Exported with the :colours tag.

=cut

# return the luminance of the colour (RGB)
sub _luminance 
{ 
    (0.212671 * $_[0] + 0.715160 * $_[1] + 0.072169 * $_[2])/0xFF
}

# return the hue of the colour (RGB)
sub _hue 
{ 
    ($_[0] + $_[1] + $_[2])/(3 * 0xFF) 
}

=head2 add_colour(colourname => [$r, $g, $b]) or
add_colour('#7fe310')

Self-explanatory.
Exported with the :colours tag.

=cut

sub add_colour
{
    my $name = shift;
    my $val  = shift;

    if (!defined $val)
    {
        my @rgb = hex2rgb($name) or return;
        $val = [@rgb];
    }

    if (ref $val && ref $val eq 'ARRAY')
    {
        $RGB{$name} = [@{$val}];
        return $name;
    }

    return;
}

=head2 rgb2hex($red, $green, $blue)

=head2 hex2rgb('#7fe310')

These functions translate a list of RGB values into a hexadecimal
string, as is commonly used in HTML and the Image::Magick API, and vice
versa.
Exported with the :convert tag.

=cut

# Color translation
sub rgb2hex
{
    return unless @_ == 3;
    my $color = '#';
    foreach my $cc (@_)
    {
        $color .= sprintf("%02x", $cc);
    }
    return $color;
}

sub hex2rgb
{
    my $clr = shift;
    my @rgb = $clr =~ /^#([a-f0-9]{2})([a-f0-9]{2})([a-f0-9]{2})$/i;
    return unless @rgb;
    return map { hex $_ } @rgb;
}

=head2 read_rgb( F<file name> )

Reads in colours from a rgb file as used by the X11 system.

Doing something like:

    use GD::Graph::bars;
    use GD::Graph::colour;

    GD::Graph::colour::read_rgb("rgb.txt") or die "cannot read colours";

Will allow you to use any colours defined in rgb.txt in your graph.
Exported with the :files tag.

=cut

#
# Read a rgb.txt file (X11)
#
# Expected format of the file:
#
# R G B colour name
#
# Fields can be separated by any number of whitespace
# Lines starting with an exclamation mark (!) are comment and 
# will be ignored.
#
# returns number of colours read

sub read_rgb($) # (filename)
{
    my $fn = shift;
    my $n = 0;
    my $line;