NAME
    Color::RGB::Util - Utilities related to RGB colors

VERSION
    This document describes version 0.606 of Color::RGB::Util (from Perl
    distribution Color-RGB-Util), released on 2021-08-06.

SYNOPSIS
     use Color::RGB::Util qw(
         assign_rgb_color
         assign_rgb_dark_color
         assign_rgb_light_color
         int2rgb
         mix_2_rgb_colors
         mix_rgb_colors
         rand_rgb_color
         rand_rgb_colors
         reverse_rgb_color
         rgb2grayscale
         rgb2int
         rgb2sepia
         rgb_diff
         rgb_distance
         rgb_is_dark
         rgb_is_light
         rgb_luminance
         tint_rgb_color
     );

     say assign_rgb_color("foo");                    # 0b5d33
     say assign_rgb_dark_color("foo");               # 0b5d33
     say assign_rgb_light_color("foo");              # 85ae99

     say int2rgb(0xffffff);                          # ffffff

     say mix_2_rgb_colors('#ff0000', '#ffffff');     # pink (red + white)
     say mix_2_rgb_colors('ff0000', 'ffffff', 0.75); # pink with a whiter shade

     say mix_rgb_colors('ff0000', 1, 'ffffff', 1);   # pink (red + white 1 : 1)
     say mix_rgb_colors('ff0000', 1, 'ffffff', 3);   # pink with a whiter shade (red + white 1 : 3)
     say mix_rgb_colors('ff0000', 1, 'ffffff', 1, '0000ff', 0.5);   # bluish pink

     say rand_rgb_color();
     say rand_rgb_color('000000', '333333');         # limit range

     say rand_rgb_colors(
           {light_color => 1, avoid_colors=>[qw/ffffff ffcc00 ff00cc/],
           3);                                       # ("e9f3d7", "e0bbcc", "63f88c")

     say reverse_rgb_color('0033CC');                # => ffcc33

     say rgb2grayscale('0033CC');                     # => 555555 # default 'average' algo
     say rgb2grayscale('0033CC', 'weighted_average'); # => 353535

     say rgb2int("ffffff");                          # 16777215 (which is 0xffffff)

     say rgb2sepia('0033CC');                        # => 4d4535

     say rgb_distance('000000', '000000')            # => 0
     say rgb_distance('01f000', '04f400')            # => 5
     say rgb_distance('ffff00', 'ffffff')            # => 255

     say rgb_diff('000000', '000000');               # => 0
     say rgb_diff('01f000', '04f400');               # => 5
     say rgb_diff('ffff00', 'ffffff');               # => 255
     say rgb_diff('000000', '000000', 'approx1');    # => 0
     say rgb_diff('01f000', '04f400', 'approx1');    # => 9.06
     say rgb_diff('ffff00', 'ffffff', 'approx1');    # => 360.98

     say rgb_is_dark('404040');                      # => 1
     say rgb_is_dark('a0a0a0');                      # => 0
     say rgb_is_light('404040');                     # => 0
     say rgb_is_light('a0a0a0');                     # => 1

     say rgb_luminance('d090aa');                    # => ffcc33

     say tint_rgb_color('#ff8800', '#0033cc');       # => b36e3c

DESCRIPTION
FUNCTIONS
    None are exported by default, but they are exportable.

  assign_rgb_color
    Usage:

     my $rgb = assign_rgb_color($str);

    Map a string to an RGB color. This is done by producing SHA-1 digest
    (160bit, 20 bytes) of the string, then taking the first, 10th, and last
    byte to become the RGB color.

    See also: "assign_rgb_dark_color" and "assign_rgb_light_color".

  assign_rgb_dark_color
    Like "assign_rgb_color" except that it will make sure the assigned color
    is dark.

  assign_rgb_light_color
    Like "assign_rgb_color" except that it will make sure the assigned color
    is light.

  hsl2hsv
    Usage:

     my $hsl = hsl2hsv("0 1 0.5"); # => "0 1 1"

    Convert HSL to HSV.

    See also: "hsv2hsl".

  hsl2rgb
    Usage:

     my $rgb = hsl2rgb("0 1 0.5"); # => ff0000

    Convert HSL to RGB. HSL should be given in a whitespace-separated H,S,L
    values e.g. "0 1 0.5". H (hue degree) has a range from 0-360 where 0 is
    red, 120 is green, 240 is blue and 360 is back to red. S (saturation)
    has a range from 0-1 where 0 is gray and 1 is fully saturated hue. L
    (lumination) has a range from 0-1 where 0 is fully black, 0.5 fully
    saturated, and 1 is fully white.

    See also "rgb2hsl".

  hsv2hsl
    Usage:

     my $hsl = hsv2hsl("0 1 1"); # => "0 1 0.5"

    Convert HSV to HSL.

    See also "hsl2hsv".

  hsv2rgb
    Usage:

     my $rgb = hsv2rgb("0 1 1"); # => ff0000

    Convert HSV to RGB. HSV should be given in a whitespace-separated H,S,V
    values e.g. "0 1 1". H (hue degree) has a range from 0-360 where 0 is
    red, 120 is green, 240 is blue and 360 is back to red. S (saturation)
    has a range from 0-1 where 0 is gray and 1 is fully saturated hue. V
    (value) has a range from 0-1 where 0 is black and 1 is white.

    See also "rgb2hsv".

  int2rgb
    Usage:

     my $rgb = int2rgb(0xffffff); # => ffffff

    Convert integer to RGB string.

    See also "rgb2int".

  mix_2_rgb_colors
    Usage:

     my $mixed_rgb = mix_2_rgb_colors($rgb1, $rgb2, $pct);

    Mix 2 RGB colors. $pct is a number between 0 and 1, by default 0.5
    (halfway), the closer to 1 the closer the resulting color to $rgb2.

    See also "mix_rgb_colors", "tint_rgb_color".

  mix_rgb_colors
    Usage:

     my $mixed_rgb = mix_rgb_colors($color1, $weight1, $color2, $weight2, ...);

    Mix several RGB colors.

    See also "mix_2_rgb_colors".

  rand_rgb_color
    Usage:

     my $rgb = rand_rgb_color([ $low_limit [ , $high_limit ] ]);

    Generate a random RGB color. You can specify the limit. Otherwise, they
    default to the full range (000000 to ffffff).

    See also "rand_rgb_colors".

  rand_rgb_colors
    Usage:

     my @rgbs = rand_rgb_colors([ \%opts ], $num=1);

    Produce $num random RGB colors, with some options. It does not (yet)
    create a palette of optimally distinct colors, but will make reasonable
    attempt to make the colors different from one another.

    Known options:

    *   light_color

        Boolean, default true. By default, this function will create light
        RGB colors, assuming the background color is dark, which is often
        the case in terminal. If this option is set to false, will create
        dark colors instead, If this option is set to undef, will create
        both dark and light colors.

    *   avoid_colors

        Arrayref or hashref. List of colors to be avoided. You can put, for
        example, colors that you've already assigned/picked for your palette
        and don't want to use again.

    *   max_attempts

        Uint, default 1000. Number of attempts to try generating the next
        random color if the generated color is rejected because it is
        light/dark, or because it's in "avoid_colors".

        When the number of attempts has been exceeded, the generated color
        is used anyway.

    *   hash_prefix

        Whether to add hash prefix to produced color codes ("#123456") or
        not ("123456").

    See also "rand_rgb_color".

  reverse_rgb_color
    Usage:

     my $reversed = reverse_rgb_color($rgb);

    Reverse $rgb.

  rgb2grayscale
    Usage:

     my $rgb_gs = rgb2grayscale($rgb [ , $algo ]);

    Convert $rgb to grayscale RGB value. There are several algorithms
    ($algo) to choose from:

    *   average

        The Average method takes the average value of R, G, and B as the
        grayscale value.

         Grayscale = (R + G + B ) / 3.

        The average method is simple but does not take into account the
        non-linearity of human vision (eyes are most sensitive to green,
        less to red, least to blue).

    *   weighted_average

        This method gives weights to each of red, green, blue elements to
        take into account the sensitivity of human eyes.

         Grayscale  = 0.299R + 0.587G + 0.114B

    See also rgb2sepia.

  rgb2hsl
    Usage:

     my $hsl = rgb2hsl($rgb); # example: "0 1 0.5"

    Convert RGB (0-255) to HSL. The result is a space-separated H, S, L
    values.

    See also "hsl2rgb".

  rgb2hsv
    Usage:

     my $hsv = rgb2hsv($rgb); # example: "0 1 255"

    Convert RGB (0-255) to HSV. The result is a space-separated H, S, V
    values.

    See also "hsv2rgb".

  rgb2int
    Usage:

     my $int = rgb2int("ffffff"); # => 16777216, which is 0xffffff

    Convert RGB string to integer.

    See also "int2rgb".

  rgb2sepia
    Usage:

     my $rgb_sepia = rgb2sepia($rgb);

    Convert $rgb to sepia tone RGB value.

    See also rgb2grayscale.

  rgb_diff
    Usage:

     my $dist = rgb_diff($rgb1, $rgb2[ , $algo ])

    Calculate difference between two RGB colors, using one of several
    algorithms.

    *   euclidean

        The default. It calculates the distance as:

         ( (R1-R2)**2 + (G1-G2)**2 + (B1-B2)**2 )**0.5

        which is the same as what "rgb_distance"() would produce.

    *   approx1

        This algorithm, described in [1] as "a low cost approximation" and
        "a combination both weighted Euclidean distance functions, where the
        weight factors depend on how big the 'red' component of the colour
        is" with "results that are very close to L*u*v" and "a more stable
        algorithm", uses the following formula:

         ( 2*(R1-R2)**2 + 4*(G1-G2)**2 + 3*(B1-B2)**2 + Rm*((R1-R2)**2 - (B1-B2)**2)/256 )**0.5

        where, Rm or "R mean" is (R1+R2)/2.

    *   approx2

        Like "approx1", but uses this formula:

         ( 2*(R1-R2)**2 + 4*(G1-G2)**2 + 3*(B1-B2)**2 )**0.5  # if Rm < 128
         ( 3*(R1-R2)**2 + 4*(G1-G2)**2 + 2*(B1-B2)**2 )**0.5  # otherwise

    *   hsv_euclidean

        Convert the RGB values to HSV, then calculate the HSV distance.
        Please see source code for details.

    *   hsv_hue1

        Like "hsv_euclidean" but puts more emphasis on hue difference. This
        algorithm is used, for example, by Color::ANSI::Util when mapping
        RGB 24bit color to the "closest" the ANSI 256-color or 16-color.
        This algorithm tends to choose the hued colors instead of favoring
        to fallback on white/gray, which is more preferred.

    TODO: redmean low-cost approximation, CMC l:c.

    For more about color difference, try reading
    <https://en.wikipedia.org/wiki/Color_difference>.

    [1] https://www.compuphase.com/cmetric.htm

    See also rgb_distance.

  rgb_distance
    Usage:

     my $dist = rgb_distance($rgb1, $rgb2)

    Calculate the euclidean RGB distance, using this formula:

     ( (R1-R2)**2 + (G1-G2)**2 + (B1-B2)**2 )**0.5

    For example, the distance between "000000" and "ffffff" is ~441.67,
    while the distance between "ffff00" and "ffffff" is 255.

    See also rgb_diff.

  rgb_is_dark
    Usage:

     my $is_dark = rgb_is_dark($rgb)

    Return true if $rgb is a "dark" color, which is determined by checking
    if the RGB distance to "000000" is smaller than to "ffffff".

    See also "rgb_is_light".

  rgb_is_light
    Usage:

     my $is_light = rgb_is_light($rgb)

    Return true if $rgb is a "light" color, which is determined by checking
    if the RGB distance to "000000" is larger than to "ffffff".

    See also "rgb_is_dark".

  rgb_luminance
    Usage:

     my $luminance = rgb_luminance($rgb);

    Calculate standard/objective luminance from RGB value using this
    formula:

     (0.2126*R) + (0.7152*G) + (0.0722*B)

    where R, G, and B range from 0 to 1. Return a number from 0 to 1.

  tint_rgb_color
    Usage:

     my $new_rgb = tint_rgb_color($rgb, $tint_rgb, $pct)

    Tint $rgb with $tint_rgb. $pct is by default 0.5. It is similar to
    mixing, but the less luminance the color is the less it is tinted with
    the tint color. This has the effect of black color still being black
    instead of becoming tinted.

    See also mix_2_rgb_colors, mix_rgb_colors.

HOMEPAGE
    Please visit the project's homepage at
    <https://metacpan.org/release/Color-RGB-Util>.

SOURCE
    Source repository is at
    <https://github.com/perlancar/perl-SHARYANTO-Color-Util>.

BUGS
    Please report any bugs or feature requests on the bugtracker website
    <https://rt.cpan.org/Public/Dist/Display.html?Name=Color-RGB-Util>

    When submitting a bug or request, please include a test-file or a patch
    to an existing test-file that illustrates the bug or desired feature.

SEE ALSO
    Color::ANSI::Util

AUTHOR
    perlancar <perlancar@cpan.org>

CONTRIBUTORS
    *   ryosh2 (on pc-office) <ryosharyanto@gmail.com>

    *   Steven Haryanto <sharyanto@cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2021, 2020, 2019, 2018, 2015, 2014, 2013
    by perlancar@cpan.org.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

