HSL2RGB converter source code (Perl)

Cleaning up my web space I found an old code to convert HSL triplets (Hue Saturation Lightness) to RGB (Red Blue Green). I think the code comes from the Gimp source code and was ported to Perl, but it’s so simple I think you can port easily everywhere.

So, why do you need to convert HSL to RGB? HSL values are more human understandable, so there a good choice for a color picket or something similar. But most graphic application require RGB values which are mostly used by computers.

 

And here is the code:

hsl_to_rgb($h, $s, $l); # Values in 0-255 range

sub hsl_to_rgb {
 my $h = $_[0]/255;
 my $s = $_[1]/255;
 my $l = $_[2]/255;
 my $r, $g, $b;

 if ($h<1/6) {
 $r = 1; $g = 6*$h; $b = 0;
 $g = $g*$s + 1 - $s; $b = $b*$s + 1 - $s;
 $r = $r*$l; $g = $g*$l; $b = $b*$l;
 } elsif ($h<1/3) {
 $r = 1-6*($h - 1/6); $g = 1; $b = 0;
 $r = $r*$s + 1 - $s; $b = $b*$s + 1 - $s;
 $r = $r*$l; $g = $g*$l; $b = $b*$l;
 } elsif ($h<1/2) {
 $r = 0; $g = 1; $b = 6*($h - 1/3);
 $r = $r*$s + 1 - $s; $b = $b*$s + 1 - $s;
 $r = $r*$l; $g = $g*$l; $b = $b*$l;
 } elsif ($h<2/3) {
 $r = 0; $g = 1-6*($h - 1/2); $b = 1;
 $r = $r*$s + 1 - $s; $g = $g*$s + 1 - $s;
 $r = $r*$l; $g = $g*$l; $b = $b*$l;
 } elsif ($h<5/6) {
 $r = 6*($h - 2/3); $g = 0; $b = 1;
 $r = $r*$s + 1 - $s; $g = $g*$s + 1 - $s;
 $r = $r*$l; $g = $g*$l; $b = $b*$l;
 } else {
 $r = 1; $g = 0; $b = 1-6*($h - 5/6);
 $g = $g*$s + 1 - $s; $b = $b*$s + 1 - $s;
 $r = $r*$l; $g = $g*$l; $b = $b*$l;
 }
 $r = int $r * 255;
 $g = int $g * 255;
 $b = int $b * 255;

 return {r => $r, g => $g, b => $b);
}

Enjoy!

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