Graphics::Toolkit::Color - color palette creation helper


    my $red = Graphics::Toolkit::Color->new('red'); # create color object
    say $red->add('blue')->name;                    # mix in RGB: 'magenta'
    Graphics::Toolkit::Color->new( 0, 0, 255)->hsl; # 240, 100, 50 = blue
    $blue->blend_with({H=> 0, S=> 0, L=> 80}, 0.1); # mix blue with a little grey in HSL
    $red->rgb_gradient_to( '#0000FF', 10);          # 10 colors from red to blue
    $red->complementary( 3 );                       # get fitting red green and blue


Read only color holding objects with no additional dependencies. Create them in many different ways (see section CONSTRUCTOR). Access its values via methods from section GETTER or create related color objects via methods listed under METHODS.

Humans access colors on hardware level (eye) in RGB, on cognition level in HSL (brain) and on cultural level (language) with names. Having easy access to all three and some color math should enable you to get the color palette you desire quickly.


There are many options to create a color objects. In short you can either use the name of a predefined constant or provide values in RGB or HSL color space.

new( 'name' )

Get a color by providing a name from the X11, HTML (CSS) or SVG standard or a Pantone report. UPPER or CamelCase will be normalized to lower case and inserted underscore letters ('_') will be ignored as perl does in numbers (1_000 == 1000). All available names are listed under Graphics::Toolkit::Color::Constant.

    my $color = Graphics::Toolkit::Color->new('Emerald');
    my @names = Graphics::Toolkit::Color::Constant::all_names(); # select from these

new( 'scheme:color' )

Get a color by name from a specific scheme or standard as provided by an external module Graphics::ColorNames::* , which has to be installed separately. * is a placeholder for the pallet name, which might be: Crayola, CSS, EmergyC, GrayScale, HTML, IE, Mozilla, Netscape, Pantone, PantoneReport, SVG, VACCC, Werner, Windows, WWW or X. In ladder case Graphics::ColorNames::X has to be installed. You can get them all at once via Bundle::Graphics::ColorNames. The color name will be normalized as above.

    my $color = Graphics::Toolkit::Color->new('SVG:green');
    my @s = Graphics::ColorNames::all_schemes();          # look up the installed

new( '#rgb' )

Color definitions in hexadecimal format as widely used in the web, are also acceptable.

    my $color = Graphics::Toolkit::Color->new('#FF0000');
    my $color = Graphics::Toolkit::Color->new('#f00');    # works too

new( [$r, $g, $b] )

Triplet of integer RGB values ("red", "green" and "blue" : 0 .. 255). Out of range values will be corrected to the closest value in range.

    my $red = Graphics::Toolkit::Color->new( 255, 0, 0 );
    my $red = Graphics::Toolkit::Color->new([255, 0, 0]); # does the same

new( {r => $r, g => $g, b => $b} )

Hash with the keys 'r', 'g' and 'b' does the same as shown in previous paragraph, only more declarative. Casing of the keys will be normalised and only the first letter of each key is significant.

    my $red = Graphics::Toolkit::Color->new( r => 255, g => 0, b => 0 );
    my $red = Graphics::Toolkit::Color->new({r => 255, g => 0, b => 0}); # works too
    ... Color->new( Red => 255, Green => 0, Blue => 0);   # also fine

new( {h => $h, s => $s, l => $l} )

To define a color in HSL space, with values for "hue", "saturation" and "lightness", use the following keys, which will be normalized as decribed in previous paragraph. Out of range values will be corrected to the closest value in range. Since "hue" is a polar coordinate, it will be rotated into range, e.g. 361 = 1.

    my $red = Graphics::Toolkit::Color->new( h =>   0, s => 100, b => 50 );
    my $red = Graphics::Toolkit::Color->new({h =>   0, s => 100, b => 50}); # good too
    ... ->new( Hue => 0, Saturation => 100, Lightness => 50 ); # also fine


If writing Graphics::Toolkit::Color-new(...> is too much typing for you or takes to much space, import the subroutine color, which takes all the same arguments as described above.

    use Graphics::Toolkit::Color qw/color/;
    my $green = color('green');
    my $darkblue = color([20, 20, 250]);


are read only methods - giving access to different parts of the objects data.


String with name of the color in the X11 or HTML (SVG) standard or the Pantone report. The name will be found and filled in, even when the object is created with RGB or HSL values. If the color is not found in any of the mentioned standards, it returns an empty string. All names are at: "NAMES" in Graphics::Toolkit::Color::Constant


String that can be serialized back into a color object (recreated by Graphics::Toolkit::Color->new( $string )). It is either the color "name" (if color has one) or result of "rgb_hex".


Integer between 0 .. 255 describing the red portion in RGB space. Higher value means more color and an lighter color.


Integer between 0 .. 255 describing the green portion in RGB space. Higher value means more color and an lighter color.


Integer between 0 .. 255 describing the blue portion in RGB space. Higher value means more color and an lighter color.


Integer between 0 .. 359 describing the angle (in degrees) of the circular dimension in HSL space named hue. 0 approximates red, 30 - orange, 60 - yellow, 120 - green, 180 - cyan, 240 - blue, 270 - violet, 300 - magenta, 330 - pink. 0 and 360 point to the same coordinate. This module only outputs 0, even if accepting 360 as input.


Integer between 0 .. 100 describing percentage of saturation in HSL space. 0 is grey and 100 the most colorful (except when lightness is 0 or 100).


Integer between 0 .. 100 describing percentage of lightness in HSL space. 0 is always black, 100 is always white and 50 the most colorful (depending on "hue" value) (or grey - if saturation = 0).


List (no ARRAY reference) with values of "red", "green" and "blue".


List (no ARRAY reference) with values of "hue", "saturation" and "lightness".


String starting with character '#', followed by six hexadecimal lower case figures. Two digits for each of "red", "green" and "blue" value - the format used in CSS (#rrggbb).


Reference to a HASH containing the keys 'red', 'green' and 'blue' with their respective values as defined above.


Reference to a HASH containing the keys 'hue', 'saturation' and 'lightness' with their respective values as defined above.


create new, related color (objects) or compute similarity of colors


A number that measures the distance (difference) between two colors: 1. the calling object (C1) and 2. a provided first argument C2 - color object or scalar data that is acceptable by new method : name or #hex or [$r, $g, $b] or {...} (see chapter CONSTRUCTOR).

If no second argument is provided, than the difference is the Euclidean distance in cylindric HSL space. If second argument is 'rgb' or 'RGB', then its the Euclidean distance in RGB space. But als subspaces of both are possible, as r, g, b, rg, rb, gb, h, s, l, hs, hl, and sl.

    my $d = $blue->distance_to( 'lapisblue' ); # how close to lapis color?
    # how different is my blue value to airy_blue
    $d = $blue->distance_to( 'airyblue', 'Blue'); # same amount of blue?
    $d = $color->distance_to( $c2, 'Hue' ); # same hue ?
    $d = $color->distance_to( [10, 32, 112 ], 'rgb' );
    $d = $color->distance_to( { Hue => 222, Sat => 23, Light => 12 } );


Create a Graphics::Toolkit::Color object, by adding any RGB or HSL values to current color. (Same rules apply for key names as in new - values can be negative.) RGB and HSL can be combined, but please note that RGB are applied first.

If the first argument is a Graphics::Toolkit::Color object, than RGB values will be added. In that case an optional second argument is a factor (default = 1), by which the RGB values will be multiplied before being added. Negative values of that factor lead to darkening of result colors, but its not subtractive color mixing, since this module does not support CMY color space. All RGB operations follow the logic of additive mixing, and the result will be rounded (trimmed), to keep it inside the defined RGB space.

    my $blue = Graphics::Toolkit::Color->new('blue');
    my $darkblue = $blue->add( Lightness => -25 );
    my $blue2 = $blue->add( blue => 10 );
    $blue->distance( $blue2 );           # == 0, can't get bluer than blue
    my $color = $blue->add( $c2, -1.2 ); # subtract color c2 with factor 1.2


Create Graphics::Toolkit::Color object, that is the average of two colors in HSL space: 1. the calling object (C1) and 2. a provided argument C2 (object or a refrence to data that is acceptable definition).

The second argument is the blend ratio, which defaults to 0.5 ( 1:1 ). 0 represents here C1 and 1 C2. Numbers below 0 and above 1 are possible, and will be applied, as long the result is inside the finite HSL space. There is a slight overlap with the add method which mostly operates in RGB (unless told so), while this method always operates in HSL space.

    my $c = $color->blend_with( Graphics::Toolkit::Color->new('silver') );
    $color->blend_with( 'silver' );                        # same thing
    $color->blend_with( [192, 192, 192] );                 # still same
    my $difference = $color->blend_with( $c2, -1 );


Creates a gradient (a list of colors that build a transition) between current (C1) and a second, given color (C2).

The first argument is C2. Either as an Graphics::Toolkit::Color object or a scalar (name, hex or reference), which is acceptable to a constructor.

Second argument is the number $n of colors, which make up the gradient (including C1 and C2). It defaults to 3. These 3 colors C1, C2 and a color in between, which is the same as the result of method blend_with.

Third argument is also a positive number $p, which defaults to one. It defines the dynamics of the transition between the two colors. If $p == 1 you get a linear transition - meaning the distance in RGB space is equal from one color to the next. If $p != 1, the formula $n ** $p starts to create a parabola function, which defines a none linear mapping. For values $n > 1 the transition starts by sticking to C1 and slowly getting faster and faster toward C2. Values $n < 1 do the opposite: starting by moving fastest from C1 to C2 (big distances) and becoming slower and slower.

    my @colors = $c->rgb_gradient_to( $grey, 5 );         # we turn to grey
    @colors = $c1->rgb_gradient_to( [14,10,222], 10, 3 ); # none linear gradient


Same as "rgb_gradient_to" (what you normally want), but in HSL space.


Creates a set of complementary colors. It accepts 3 numerical arguments: n, delta_S and delta_L.

Imagine an horizontal circle in HSL space, whith a center in the (grey) center column. The saturation and lightness of all colors on that circle is the same, they differ only in hue. The color of the current color object ($self a.k.a C1) lies on that circle as well as C2, which is 180 degrees (half the circumference) apposed to C1.

This circle will be divided in $n (first argument) equal partitions, creating $n equally distanced colors. All of them will be returned, as objects, starting with C1. However, when $n is set to 1 (default), the result is only C2, which is THE complementary color to C1.

The second argument moves C2 along the S axis (both directions), so that the center of the circle is no longer in the HSL middle column and the complementary colors differ in saturation. (C1 stays unmoved. )

The third argument moves C2 along the L axis (vertical), which gives the circle a tilt, so that the complementary colors will differ in lightness.

    my @colors = $c->complementary( 3, +20, -10 );



Copyright 2022 Herbert Breunung.

This program is free software; you can redistribute it and/or modify it under same terms as Perl itself.


Herbert Breunung, <>