use strict;
use warnings;
-use List::Util 'min';
+use List::Util qw( min max );
-our $VERSION = '1.00';
+our $VERSION = '1.05';
+
+# ITU-R recommendation 601 luma co-efficients
+our $kr = .299;
+our $kb = .114;
+our $kg = 1 - $kb - $kr;
+
+my $PI = 2 * atan2 1, 0;
sub new {
my $class = shift;
bless \@rgb, $class;
}
+sub newyuv {
+ # convert from YPbPr values -1..1
+ my $class = shift;
+ my ($y, $cb, $cr) = @_;
+
+ my @rgb = map { max(0, min(255, $_ * 255)) } (
+ $y + $cr,
+ $y - $cb * (1 - $kb) * $kb/$kg - $cr * $kr/$kg,
+ $y + $cb * (1 - $kb) ,
+ );
+ bless \@rgb, $class;
+}
+
+sub newyuv8 {
+ # convert from YPbPr values 0..255 (or hex string)
+ my $class = shift;
+ my ($y, $cb, $cr) = @_ >= 3 ? @_ : (map {hex} $_[0] =~ /(..)/g);
+
+ $_ -= 128 for $cb, $cr;
+ $_ /= 255 for $y, $cb, $cr;
+
+ $class->newyuv($y, $cb, $cr);
+}
+
sub luminance {
- # perceived brightness (using ITU-R recommendation 601 luma co-efficients)
+ # perceived brightness
+ my ($r, $g, $b) = @{ $_[0] };
+ return $r*$kr + $g*$kg + $b*$kb;
+}
+
+sub hue {
+ # colour shift (red = 0 .. 1)
my ($r, $g, $b) = @{ $_[0] };
- return $r*.299 + $g*.587 + $b*.114;
+ my $hue = atan2 sqrt(3) * ($g - $b), $r*2 - $g - $b;
+ $hue /= $PI * 2; # -.5 .. .5
+ $hue++ if $hue < 0; # fp $hue %= 1
+ return $hue;
+}
+
+sub hsv {
+ my ($rgb) = @_;
+ my $v = max(@{$rgb});
+ return $rgb->hue, abs(min(@{$rgb}) - $v), $v;
}
sub rgb24 {