convert hex to hsl

hex-to-hsl.php

<?php

// http://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/

// convert hex to hsl
$hex = str_split(ltrim('#0099cc', '#'), 2);

// convert the rgb values to the range 0-1
$rgb = array_map(function($part) {
  return hexdec($part) / 255;
}, $hex);

// find the minimum and maximum values of r, g and b
$min = min($rgb);
$max = max($rgb);

// calculate the luminace value by adding the max and min values and divide by 2
$l = ($min + $max) / 2;

if ($max === $min) {
  $h = $s = 0;
} else {
  if ($l < 0.5) {
    $s = ($max - $min) / ($max + $min);
  } elseif ($l > 0.5) {
    $s = ($max - $min) / (2 - $max - $min);
  }

  if ($max === $rgb[0]) {
    $h = ($rgb[1]- $rgb[2]) / ($max -$min);
  } elseif ($max === $rgb[1]) {
    $h = 2 + ($rgb[2]- $rgb[0]) / ($max -$min);
  } elseif ($max === $rgb[2]) {
    $h = 4 + ($rgb[0]- $rgb[1]) / ($max -$min);
  }

  $h = $h * 60;

  if ($h < 0) {
    $h = $h + 360;
  }
}