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# You may distribute under the terms of either the GNU General Public License
# or the Artistic License (the same terms as Perl itself)
#
# (C) Paul Evans, 2009-2022 -- leonerd@leonerd.org.uk
package # hide from CPAN
Convert::Color::HueChromaBased;
use v5.14;
use warnings;
use base qw( Convert::Color );
# For converting degrees to radians
# atan2(1,0) == PI/2
use constant PIover180 => atan2(1,0) / 90;
# No space name since we're not a complete space
use List::Util qw( max min );
# HSV and HSL are related, using some common elements.
# See also
# http://en.wikipedia.org/wiki/HSV_color_space
sub _hue_min_max
{
my $class = shift;
my ( $r, $g, $b ) = @_;
my $max = max $r, $g, $b;
my $min = min $r, $g, $b;
my $hue;
if( $max == $min ) {
$hue = 0;
}
elsif( $max == $r ) {
$hue = 60 * ( $g - $b ) / ( $max - $min );
}
elsif( $max == $g ) {
$hue = 60 * ( $b - $r ) / ( $max - $min ) + 120;
}
elsif( $max == $b ) {
$hue = 60 * ( $r - $g ) / ( $max - $min ) + 240;
}
return ( $hue, $min, $max );
}
# Useful for distance calculations - calculates the square of the distance
# between two points in polar space
sub _huechroma_dst_squ
{
my ( $col1, $col2 ) = @_;
my $r1 = $col1->chroma;
my $r2 = $col2->chroma;
my $dhue = $col1->hue - $col2->hue;
# Square of polar distance
return $r1*$r1 + $r2*$r2 - 2*$r1*$r2*cos( $dhue * PIover180 );
}
0x55AA;
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