RGBからHSVに変換する（perl）

rgb_to_hsv.pl

package RGBtoHSV;

use strict;
use warnings;

sub rgb_to_hsv {
    my $rgb_ref = shift;
    my $max_c = get_max( $rgb_ref );
    my $min_c = get_min( $rgb_ref );

    if ( is_white($rgb_ref) ) {
        return {
            H => 0,
            S => 0,
            V => 255,
        };
    }
    elsif ( is_black($rgb_ref) ) {
        return {
            H => 0,
            S => 0,
            V => 0,
        };
    }
    else {
        return get_hsv_from_rgb( $rgb_ref, $max_c, $min_c );
    }
}
sub is_black {
    my $rgb_ref = shift;

    if ( 0 == $rgb_ref->{R} && 0 == $rgb_ref->{G} && 0 == $rgb_ref->{B} ) {
        return 1;
    }
    else {
        return;
    }
}
sub is_white {
    my $rgb_ref = shift;

    if ( 255 == $rgb_ref->{R} && 255 == $rgb_ref->{G} && 255 == $rgb_ref->{B} ) {
        return 1;
    }
    else {
        return;
    }
}
sub get_hsv_from_rgb {
    my $rgb_ref = shift;
    my $max_c   = shift;
    my $min_c   = shift;

    return {
        H => calc_H( $rgb_ref, $max_c, $min_c ),
        S => calc_S( $rgb_ref, $max_c, $min_c ),
        V => calc_V( $rgb_ref, $max_c ),
    };
}
sub calc_H {
    my ($rgb_ref, $max_c, $min_c) = @_;
    my ($R, $G, $B, $MAX, $MIN) = ( $rgb_ref->{R}, $rgb_ref->{G}, $rgb_ref->{B}, $rgb_ref->{$max_c}, $rgb_ref->{$min_c} );

    my $H
        = $max_c eq 'R' ? 60 * ( ($G - $B) / ($MAX - $MIN) ) + 0
        : $max_c eq 'G' ? 60 * ( ($B - $R) / ($MAX - $MIN) ) + 120
        :                 60 * ( ($R - $G) / ($MAX - $MIN) ) + 240
        ;
    
    return $H < 0 ? $H + 360
         :          $H
         ;
}

sub calc_S {
    my ($rgb_ref, $max_c, $min_c) = @_;

    return ( $rgb_ref->{$max_c} - $rgb_ref->{$min_c} ) / $rgb_ref->{$max_c};
}

sub calc_V {
    my ($rgb_ref, $max_c) = @_;

    return $rgb_ref->{$max_c} / 255;
}

sub get_max {
    my $rgb_ref = shift;
    my $max = 0;
    my $max_name = '';

    while ( my ( $cname, $value ) = each( %$rgb_ref ) ) {
        if ( $value > $max ) {
            $max = $value;
            $max_name = $cname;
        }
    }

    return $max_name;
}
sub get_min {
    my $rgb_ref  = shift;
    my $min      = 2000000000;
    my $min_name = '';

    while ( my ( $cname, $value ) = each( %$rgb_ref ) ) {
        if ( $value < $min ) {
            $min      = $value;
            $min_name = $cname;
        }
    }

    return $min_name;
}
1;