package Color::RGB::Util;
our $AUTHORITY = 'cpan:PERLANCAR'; # AUTHORITY
our $DATE = '2020-06-08'; # DATE
our $DIST = 'Color-RGB-Util'; # DIST
our $VERSION = '0.601'; # VERSION
use 5.010001;
use strict;
use warnings;
#use List::Util qw(min);
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw(
assign_rgb_color
assign_rgb_dark_color
assign_rgb_light_color
hsl2hsv
hsl2rgb
hsv2hsl
hsv2rgb
int2rgb
mix_2_rgb_colors
mix_rgb_colors
rand_rgb_color
rand_rgb_colors
reverse_rgb_color
rgb2grayscale
rgb2hsv
rgb2hsl
rgb2int
rgb2sepia
rgb_diff
rgb_distance
rgb_is_dark
rgb_is_light
rgb_luminance
tint_rgb_color
);
my $re_rgb = qr/\A#?([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})\z/;
sub _min {
$_[0] < $_[1] ? $_[0] : $_[1];
}
sub _wrap_h {
my $h = shift;
$h %= 360 if abs($h) > 360;
$h >= 0 ? $h : 360+$h;
}
sub assign_rgb_color {
require Digest::SHA;
my ($str) = @_;
my $sha1 = Digest::SHA::sha1_hex($str);
substr($sha1, 0, 2) .
substr($sha1, 18, 2) .
substr($sha1, 38, 2);
}
sub assign_rgb_dark_color {
my $str = shift;
my $rgb = assign_rgb_color($str);
rgb_is_dark($rgb) ? $rgb : mix_2_rgb_colors($rgb, '000000');
}
sub assign_rgb_light_color {
my $str = shift;
my $rgb = assign_rgb_color($str);
rgb_is_light($rgb) ? $rgb : mix_2_rgb_colors($rgb, 'ffffff');
}
sub int2rgb {
my $int = shift;
return sprintf("%02x%02x%02x",
($int & 0xff0000) >> 16,
($int & 0x00ff00) >> 8,
($int & 0x0000ff),
);
}
sub mix_2_rgb_colors {
my ($rgb1, $rgb2, $pct) = @_;
$pct //= 0.5;
my ($r1, $g1, $b1) =
$rgb1 =~ $re_rgb or die "Invalid rgb1 color '$rgb1', must be in 'ffffff' form";
my ($r2, $g2, $b2) =
$rgb2 =~ $re_rgb or die "Invalid rgb2 color '$rgb2', must be in 'ffffff' form";
for ($r1, $g1, $b1, $r2, $g2, $b2) { $_ = hex $_ }
return sprintf("%02x%02x%02x",
$r1 + $pct*($r2-$r1),
$g1 + $pct*($g2-$g1),
$b1 + $pct*($b2-$b1),
);
}
sub mix_rgb_colors {
my (@weights, @r, @g, @b);
while (@_ >= 2) {
my ($rgb, $weight) = splice @_, 0, 2;
my ($r, $g, $b) = $rgb =~ $re_rgb
or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
push @r, hex $r;
push @g, hex $g;
push @b, hex $b;
push @weights, $weight;
}
my $tot_r = 0; for (0..$#r) { $tot_r += $r[$_]*$weights[$_] }
my $tot_g = 0; for (0..$#g) { $tot_g += $g[$_]*$weights[$_] }
my $tot_b = 0; for (0..$#b) { $tot_b += $b[$_]*$weights[$_] }
my $tot_weight = 0; $tot_weight += $_ for @weights;
die "Zero/negative total weight" unless $tot_weight > 0;
return sprintf("%02x%02x%02x",
$tot_r / $tot_weight,
$tot_g / $tot_weight,
$tot_b / $tot_weight,
);
}
sub rand_rgb_color {
my ($rgb1, $rgb2) = @_;
$rgb1 //= '000000';
my ($r1, $g1, $b1) =
$rgb1 =~ $re_rgb or die "Invalid rgb1 color '$rgb1', must be in 'ffffff' form";
$rgb2 //= 'ffffff';
my ($r2, $g2, $b2) =
$rgb2 =~ $re_rgb or die "Invalid rgb2 color '$rgb2', must be in 'ffffff' form";
for ($r1, $g1, $b1, $r2, $g2, $b2) { $_ = hex $_ }
return sprintf("%02x%02x%02x",
$r1 + rand()*($r2-$r1+1),
$g1 + rand()*($g2-$g1+1),
$b1 + rand()*($b2-$b1+1),
);
}
sub rand_rgb_colors {
my $opts = ref $_[0] eq 'HASH' ? shift : {};
my $num = shift // 1;
my $light_color = exists($opts->{light_color}) ? $opts->{light_color} : 1;
my $max_attempts = $opts->{max_attempts} // 1000;
my $avoid_colors = $opts->{avoid_colors};
my @res;
while (@res < $num) {
my $num_attempts = 0;
my $rgb;
while (1) {
$rgb = rand_rgb_color();
my $reject = 0;
REJECT: {
if ($light_color) {
do { $reject++; last } if rgb_is_dark($rgb);
} elsif (defined $light_color) {
do { $reject++; last } if rgb_is_light($rgb);
}
if ($avoid_colors && ref $avoid_colors eq 'ARRAY') {
do { $reject++; last } if grep { $rgb eq $_ } @$avoid_colors;
}
if ($avoid_colors && ref $avoid_colors eq 'HASH') {
do { $reject++; last } if $avoid_colors->{$rgb}
}
} # REJECT
last if !$reject;
last if ++$num_attempts >= $max_attempts;
}
push @res, $rgb;
}
@res;
}
sub reverse_rgb_color {
my ($rgb) = @_;
my ($r, $g, $b) =
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
for ($r, $g, $b) { $_ = hex $_ }
return sprintf("%02x%02x%02x", 255-$r, 255-$g, 255-$b);
}
sub rgb2grayscale {
my ($rgb) = @_;
my ($r, $g, $b) =
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
for ($r, $g, $b) { $_ = hex $_ }
# basically we just average the R, G, B
my $avg = int(($r + $g + $b)/3);
return sprintf("%02x%02x%02x", $avg, $avg, $avg);
}
sub rgb2int {
my $rgb = shift;
# just to check
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
hex($rgb);
}
sub rgb2sepia {
my ($rgb) = @_;
my ($r, $g, $b) =
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
for ($r, $g, $b) { $_ = hex $_ }
# reference: http://www.techrepublic.com/blog/howdoi/how-do-i-convert-images-to-grayscale-and-sepia-tone-using-c/120
my $or = ($r*0.393) + ($g*0.769) + ($b*0.189);
my $og = ($r*0.349) + ($g*0.686) + ($b*0.168);
my $ob = ($r*0.272) + ($g*0.534) + ($b*0.131);
for ($or, $og, $ob) { $_ = 255 if $_ > 255 }
return sprintf("%02x%02x%02x", $or, $og, $ob);
}
sub rgb_diff {
my ($rgb1, $rgb2, $algo) = @_;
$algo //= 'euclidean';
my ($r1, $g1, $b1) =
$rgb1 =~ $re_rgb or die "Invalid rgb1 color '$rgb1', must be in 'ffffff' form";
my ($r2, $g2, $b2) =
$rgb2 =~ $re_rgb or die "Invalid rgb2 color '$rgb2', must be in 'ffffff' form";
for ($r1, $g1, $b1, $r2, $g2, $b2) { $_ = hex $_ }
my $dr2 = ($r1-$r2)**2;
my $dg2 = ($g1-$g2)**2;
my $db2 = ($b1-$b2)**2;
if ($algo eq 'approx1' || $algo eq 'approx2') {
my $rm = ($r1 + $r2)/2;
if ($algo eq 'approx1') {
return (2*$dr2 + 4*$dg2 + 3*$db2 + $rm*($dr2 - $db2)/256 )**0.5;
} else { # approx2
if ($rm < 128) {
return (3*$dr2 + 4*$dg2 + 2*$db2)**0.5;
} else {
return (2*$dr2 + 4*$dg2 + 3*$db2)**0.5;
}
}
} elsif ($algo eq 'hsv_euclidean' || $algo eq 'hsv_hue1') {
my $hsv1 = rgb2hsv($rgb1);
my ($h1, $s1, $v1) = split / /, $hsv1;
my $hsv2 = rgb2hsv($rgb2);
my ($h2, $s2, $v2) = split / /, $hsv2;
my $dh2 = ( _min(abs($h2-$h1), 360-abs($h2-$h1))/180 )**2;
my $ds2 = ( $s2-$s1 )**2;
my $dv2 = ( ($v2-$v1)/255.0 )**2;
if ($algo eq 'hsv_hue1') {
return (5*$dh2 + $ds2 + $dv2)**0.5;
} else { # hsv_euclidean
return ($dh2 + $ds2 + $dv2)**0.5;
}
} else { # euclidean
return ($dr2 + $dg2 + $db2)**0.5;
}
}
sub rgb_distance {
my ($rgb1, $rgb2) = @_;
my ($r1, $g1, $b1) =
$rgb1 =~ $re_rgb or die "Invalid rgb1 color '$rgb1', must be in 'ffffff' form";
my ($r2, $g2, $b2) =
$rgb2 =~ $re_rgb or die "Invalid rgb2 color '$rgb2', must be in 'ffffff' form";
for ($r1, $g1, $b1, $r2, $g2, $b2) { $_ = hex $_ }
(($r1-$r2)**2 + ($g1-$g2)**2 + ($b1-$b2)**2)**0.5;
}
sub rgb_is_dark {
my ($rgb) = @_;
rgb_distance($rgb, "000000") < rgb_distance($rgb, "ffffff") ? 1:0;
}
sub rgb_is_light {
my ($rgb) = @_;
rgb_distance($rgb, "000000") > rgb_distance($rgb, "ffffff") ? 1:0;
}
sub _rgb_luminance {
my ($r, $g, $b) = @_;
0.2126*$r/255 + 0.7152*$g/255 + 0.0722*$b/255;
}
sub rgb_luminance {
my ($rgb) = @_;
my ($r, $g, $b) =
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
for ($r, $g, $b) { $_ = hex $_ }
return _rgb_luminance($r, $g, $b);
}
sub tint_rgb_color {
my ($rgb1, $rgb2, $pct) = @_;
$pct //= 0.5;
my ($r1, $g1, $b1) =
$rgb1 =~ $re_rgb or die "Invalid rgb1 color '$rgb1', must be in 'ffffff' form";
my ($r2, $g2, $b2) =
$rgb2 =~ $re_rgb or die "Invalid rgb2 color '$rgb2', must be in 'ffffff' form";
for ($r1, $g1, $b1, $r2, $g2, $b2) { $_ = hex $_ }
my $lum = _rgb_luminance($r1, $g1, $b1);
return sprintf("%02x%02x%02x",
$r1 + $pct*($r2-$r1)*$lum,
$g1 + $pct*($g2-$g1)*$lum,
$b1 + $pct*($b2-$b1)*$lum,
);
}
sub rgb2hsl {
my ($rgb) = @_;
my ($r, $g, $b) =
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
for ($r, $g, $b) { $_ = hex($_)/255 }
my $max = $r;
my $maxc = 'r';
my $min = $r;
if ($g > $max) {
$max = $g;
$maxc = 'g';
}
if ($b > $max) {
$max = $b;
$maxc = 'b';
}
if ($g < $min) {
$min = $g;
}
if ($b < $min) {
$min = $b;
}
my ($h, $s, $l);
if ($max == $min) {
$h = 0;
} elsif ($maxc eq 'r') {
$h = 60 * (($g - $b) / ($max - $min)) % 360;
} elsif ($maxc eq 'g') {
$h = (60 * (($b - $r) / ($max - $min)) + 120);
} elsif ($maxc eq 'b') {
$h = (60 * (($r - $g) / ($max - $min)) + 240);
}
$l = ($max + $min) / 2;
if ($max == $min) {
$s = 0;
} elsif($l <= .5) {
$s = ($max - $min) / ($max + $min);
} else {
$s = ($max - $min) / (2 - ($max + $min));
}
return sprintf("%.3g %.3g %.3g", $h, $s, $l);
}
sub rgb2hsv {
my ($rgb) = @_;
my ($r, $g, $b) =
$rgb =~ $re_rgb or die "Invalid rgb color '$rgb', must be in 'ffffff' form";
for ($r, $g, $b) { $_ = hex($_)/255 }
my $max = $r;
my $maxc = 'r';
my $min = $r;
if ($g > $max) {
$max = $g;
$maxc = 'g';
}
if($b > $max) {
$max = $b;
$maxc = 'b';
}
if($g < $min) {
$min = $g;
}
if($b < $min) {
$min = $b;
}
my ($h, $s, $v);
if ($max == $min) {
$h = 0;
} elsif ($maxc eq 'r') {
$h = 60 * (($g - $b) / ($max - $min)) % 360;
} elsif ($maxc eq 'g') {
$h = (60 * (($b - $r) / ($max - $min)) + 120);
} elsif ($maxc eq 'b') {
$h = (60 * (($r - $g) / ($max - $min)) + 240);
}
$v = $max;
if($max == 0) {
$s = 0;
} else {
$s = 1 - ($min / $max);
}
return sprintf("%.3g %.3g %.3g", $h, $s, $v);
}
sub hsl2hsv {
my $hsl = shift;
my ($h, $s, $l) = split / /, $hsl;
$h>=0 && $h<=360 or $h = _wrap_h($h); $s>=0 && $s<=1 or die "Invalid S in HSL '$hsl', must be in 0-1"; $l>=0 && $l<=1 or die "Invalid L in HSL '$hsl', must be in 0-1";
my $_h = $h;
my $_s;
my $_v;
$l *= 2;
$s *= ($l <= 1) ? $l : 2-$l;
$_v = ($l+$s) / 2;
$_s = (2*$s) / ($l+$s);
"$_h $_s $_v";
}
sub hsv2hsl {
my $hsv = shift;
my ($h, $s, $v) = split / /, $hsv;
$h>=0 && $h<=360 or $h = _wrap_h($h); $s>=0 && $s<=1 or die "Invalid S in HSV '$hsv', must be in 0-1"; $v>=0 && $v<=1 or die "Invalid V in HSV '$hsv', must be in 0-1";
my $_h = $h;
my $_s = $s * $v;
my $_l = (2-$s) * $v;
$_s /= $_l <= 1 ? ($_l==0 ? 1 : $_l) : (2-$_l);
$_l /= 2;
"$_h $_s $_l";
}
sub hsl2rgb {
hsv2rgb(hsl2hsv(shift));
}
sub hsv2rgb {
my $hsv = shift;
my ($h, $s, $v) = split / /, $hsv;
$h>=0 && $h<=360 or $h = _wrap_h($h); $s>=0 && $s<=1 or die "Invalid S in HSV '$hsv', must be in 0-1"; $v>=0 && $v<=1 or die "Invalid V in HSV '$hsv', must be in 0-1";
my $i = int($h/60);
my $f = $h/60 - $i;
my $p = $v * (1-$s);
my $q = $v * (1-$f*$s);
my $t = $v * (1-(1-$f)*$s);
my ($r, $g, $b);
if ($i==0) {
$r = $v; $g = $t; $b = $p;
} elsif ($i==1) {
$r = $q; $g = $v; $b = $p;
} elsif ($i==2) {
$r = $p; $g = $v; $b = $t;
} elsif ($i==3) {
$r = $p; $g = $q; $b = $v;
} elsif ($i==4) {
$r = $t; $g = $p; $b = $v;
} else {
$r = $v; $g = $p; $b = $q;
}
return sprintf("%02x%02x%02x", $r*255, $g*255, $b*255);
}
1;
# ABSTRACT: Utilities related to RGB colors
__END__
=pod
=encoding UTF-8
=head1 NAME
Color::RGB::Util - Utilities related to RGB colors
=head1 VERSION
This document describes version 0.601 of Color::RGB::Util (from Perl distribution Color-RGB-Util), released on 2020-06-08.
=head1 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
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
=head1 DESCRIPTION
=head1 FUNCTIONS
None are exported by default, but they are exportable.
=head2 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.
=head2 assign_rgb_dark_color
Like L</assign_rgb_color> except that it will make sure the assigned color is
dark.
=head2 assign_rgb_light_color
Like L</assign_rgb_color> except that it will make sure the assigned color is
light.
=head2 hsl2hsv
Usage:
my $hsl = hsl2hsv("0 1 0.5"); # => "0 1 1"
Convert HSL to HSV.
=head2 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
L</rgb2hsl>.
=head2 hsv2hsl
Usage:
my $hsl = hsv2hsl("0 1 1"); # => "0 1 0.5"
Convert HSV to HSL.
=head2 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 L</rgb2hsv>.
=head2 int2rgb
Usage:
my $rgb = int2rgb(0xffffff); # => ffffff
Convert integer to RGB string.
=head2 mix_2_rgb_colors
Usage:
my $mixed_rgb = mix_2_rgb_colors($rgb1, $rgb2, $pct);
Mix 2 RGB colors. C<$pct> is a number between 0 and 1, by default 0.5 (halfway),
the closer to 1 the closer the resulting color to C<$rgb2>.
=head2 mix_rgb_colors
Usage:
my $mixed_rgb = mix_rgb_colors($color1, $weight1, $color2, $weight2, ...);
Mix several RGB colors.
=head2 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).
=head2 rand_rgb_colors
Usage:
my @rgbs = rand_rgb_colors([ \%opts ], $num=1);
Produce C<$num> random RGB colors, with some options. Will make reasonable
attempt to make the colors different from one another.
Known options:
=over
=item * 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.
=item * 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.
=item * 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
C<avoid_colors>.
When the number of attempts has been exceeded, the generated color is used
anyway.
=back
=head2 reverse_rgb_color
Usage:
my $reversed = reverse_rgb_color($rgb);
Reverse C<$rgb>.
=head2 rgb2grayscale
Usage:
my $rgb_gs = rgb2grayscale($rgb);
Convert C<$rgb> to grayscale RGB value.
=head2 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.
=head2 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
=head2 rgb2int
Usage:
my $int = rgb2int("ffffff"); # => 16777216, which is 0xffffff
Convert RGB string to integer.
=head2 rgb2sepia
Usage:
my $rgb_sepia = rgb2sepia($rgb);
Convert C<$rgb> to sepia tone RGB value.
=head2 rgb_diff
Usage:
my $dist = rgb_diff($rgb1, $rgb2[ , $algo ])
Calculate difference between two RGB colors, using one of several algorithms.
=over
=item * 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 L</"rgb_distance">() would produce.
=item * approx1
This 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.
=item * approx2
Like C<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
=item * hsv_euclidean
Convert the RGB values to HSV, then calculate the HSV distance. Please see
source code for details.
=item * hsv_hue1
Like C<hsv_euclidean> but puts more emphasis on hue difference. This algorithm
is used, for example, by L<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.
=back
For more about color difference, try reading
L<https://en.wikipedia.org/wiki/Color_difference>.
=head2 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.
=head2 rgb_is_dark
Usage:
my $is_dark = rgb_is_dark($rgb)
Return true if C<$rgb> is a "dark" color, which is determined by checking if the
RGB distance to "000000" is smaller than to "ffffff".
=head2 rgb_is_light
Usage:
my $is_light = rgb_is_light($rgb)
Return true if C<$rgb> is a "light" color, which is determined by checking if
the RGB distance to "000000" is larger than to "ffffff".
=head2 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.
=head2 tint_rgb_color
Usage:
my $new_rgb = tint_rgb_color($rgb, $tint_rgb, $pct)
Tint C<$rgb> with C<$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.
=head1 HOMEPAGE
Please visit the project's homepage at L<https://metacpan.org/release/Color-RGB-Util>.
=head1 SOURCE
Source repository is at L<https://github.com/perlancar/perl-SHARYANTO-Color-Util>.
=head1 BUGS
Please report any bugs or feature requests on the bugtracker website L<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.
=head1 SEE ALSO
L<Color::ANSI::Util>
=head1 AUTHOR
perlancar <perlancar@cpan.org>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 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.
=cut