PHP function to convert HSL to RGB or Hex - php

Question

Does anyone know a PHP function (for >5.3) which can convert an HSL color to either RGB or Hex? I've tried a dozen Google searches and none of the functions I have found work as expected.
It doesn't matter whether the function converts to RGB or hex because converting between those two is trivial. The inputs are HSL values for CSS (Hue: 0–360, Saturation: 0–100, Lightness: 0–100).
Edit: Specifying the input and output format would be a bonus :)

Answer 1

Taking the code from one of the answers in the link of Jim's comment (PHP HSV to RGB formula comprehension), we can compute it as follows:
<?php
$hue = 209;
$sat = 75;
$lum = 60;
$hue /= 360;
$sat /= 100;
$lum /= 100;
$result = ColorHSLToRGB($hue, $sat, $lum);
var_dump($result); echo '<br>';
printf("rgb = %d,%d,%d<br>", $result['r'], $result['g'], $result['b']);
function ColorHSLToRGB($h, $s, $l){
$r = $l;
$g = $l;
$b = $l;
$v = ($l <= 0.5) ? ($l * (1.0 + $s)) : ($l + $s - $l * $s);
if ($v > 0){
$m;
$sv;
$sextant;
$fract;
$vsf;
$mid1;
$mid2;
$m = $l + $l - $v;
$sv = ($v - $m ) / $v;
$h *= 6.0;
$sextant = floor($h);
$fract = $h - $sextant;
$vsf = $v * $sv * $fract;
$mid1 = $m + $vsf;
$mid2 = $v - $vsf;
switch ($sextant)
{
case 0:
$r = $v;
$g = $mid1;
$b = $m;
break;
case 1:
$r = $mid2;
$g = $v;
$b = $m;
break;
case 2:
$r = $m;
$g = $v;
$b = $mid1;
break;
case 3:
$r = $m;
$g = $mid2;
$b = $v;
break;
case 4:
$r = $mid1;
$g = $m;
$b = $v;
break;
case 5:
$r = $v;
$g = $m;
$b = $mid2;
break;
}
}
return array('r' => $r * 255.0, 'g' => $g * 255.0, 'b' => $b * 255.0);
}
?>
Output:
array(3) { ["r"]=> float(76.5) ["g"]=> float(155.55) ["b"]=> float(229.5) }
rgb = 76,155,229

Answer 2

Putting this together (which helped me produce this chart)
/**
* convert a HSL colorscheme to either Hexadecimal (default) or RGB.
*
* We want a method where we can programmatically generate a series of colors
* between two values (eg. red to green) which is easy to do with HSL because
* you just change the hue. (0 = red, 120 = green). You can use this function
* to convert those hsl color values to either the rgb or hexadecimal color scheme.
* e.g. You have
* hsl(50, 100%, 50%)
* To convert,
* $hex = convertHSL(50,100,50); // returns #ffd500
* or
* $rgb = convertHSL(50,100,50, false); // returns rgb(255, 213, 0)
*
* see https://coderwall.com/p/dvsxwg/smoothly-transition-from-green-to-red
* #param int $h the hue
* #param int $s the saturation
* #param int $l the luminance
* #param bool $toHex whether you want hexadecimal equivalent or rgb equivalent
* #return string usable in HTML or CSS
*/
function convertHSL($h, $s, $l, $toHex=true){
$h /= 360;
$s /=100;
$l /=100;
$r = $l;
$g = $l;
$b = $l;
$v = ($l <= 0.5) ? ($l * (1.0 + $s)) : ($l + $s - $l * $s);
if ($v > 0){
$m;
$sv;
$sextant;
$fract;
$vsf;
$mid1;
$mid2;
$m = $l + $l - $v;
$sv = ($v - $m ) / $v;
$h *= 6.0;
$sextant = floor($h);
$fract = $h - $sextant;
$vsf = $v * $sv * $fract;
$mid1 = $m + $vsf;
$mid2 = $v - $vsf;
switch ($sextant)
{
case 0:
$r = $v;
$g = $mid1;
$b = $m;
break;
case 1:
$r = $mid2;
$g = $v;
$b = $m;
break;
case 2:
$r = $m;
$g = $v;
$b = $mid1;
break;
case 3:
$r = $m;
$g = $mid2;
$b = $v;
break;
case 4:
$r = $mid1;
$g = $m;
$b = $v;
break;
case 5:
$r = $v;
$g = $m;
$b = $mid2;
break;
}
}
$r = round($r * 255, 0);
$g = round($g * 255, 0);
$b = round($b * 255, 0);
if ($toHex) {
$r = ($r < 15)? '0' . dechex($r) : dechex($r);
$g = ($g < 15)? '0' . dechex($g) : dechex($g);
$b = ($b < 15)? '0' . dechex($b) : dechex($b);
return "#$r$g$b";
} else {
return "rgb($r, $g, $b)";
}

Answer 3

My tests of all other implementations showed only weird and possibly unplausible results. Here is a PHP implementation of #Mohsen's code from https://stackoverflow.com/a/9493060/1598477. Plus a test to show the full beauty...
Sorry to cross-post this. But I really haven't seen any other implementation that gives the quality I needed.
/**
* Converts an HSL color value to RGB. Conversion formula
* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
* Assumes h, s, and l are contained in the set [0, 1] and
* returns r, g, and b in the set [0, 255].
*
* #param {number} h The hue
* #param {number} s The saturation
* #param {number} l The lightness
* #return {Array} The RGB representation
*/
function hue2rgb($p, $q, $t){
if($t < 0) $t += 1;
if($t > 1) $t -= 1;
if($t < 1/6) return $p + ($q - $p) * 6 * $t;
if($t < 1/2) return $q;
if($t < 2/3) return $p + ($q - $p) * (2/3 - $t) * 6;
return $p;
}
function hslToRgb($h, $s, $l){
if($s == 0){
$r = $l;
$g = $l;
$b = $l; // achromatic
}else{
$q = $l < 0.5 ? $l * (1 + $s) : $l + $s - $l * $s;
$p = 2 * $l - $q;
$r = hue2rgb($p, $q, $h + 1/3);
$g = hue2rgb($p, $q, $h);
$b = hue2rgb($p, $q, $h - 1/3);
}
return array(round($r * 255), round($g * 255), round($b * 255));
}
/* Uncomment to test * /
for ($i=0;$i<360;$i++) {
$rgb=hslToRgb($i/360, 1, .9);
echo '<div style="background-color:rgb(' .$rgb[0] . ', ' . $rgb[1] . ', ' . $rgb[2] . ');padding:2px;"></div>';
}
/* End Test */

Answer 4

The PEAR package Image_Color2 has methods to transform between color models - see convertTo.

Answer 5

Here is my solution
HSV value restrictions: $H [0-359], $S [0-100], $V [0-100]
function hsv_to_rgb($iH, $iS, $iV) {
if($iH < 0) $iH = 0;
if($iH > 360) $iH = 360;
if($iS < 0) $iS = 0;
if($iS > 100) $iS = 100;
if($iV < 0) $iV = 0;
if($iV > 100) $iV = 100;
$dS = $iS/100.0;
$dV = $iV/100.0;
$dC = $dV*$dS;
$dH = $iH/60.0;
$dT = $dH;
while($dT >= 2.0) $dT -= 2.0; // php modulus does not work with float
$dX = $dC*(1-abs($dT-1)); // as used in the Wikipedia link
switch($dH) {
case($dH >= 0.0 && $dH < 1.0):
$dR = $dC; $dG = $dX; $dB = 0.0; break;
case($dH >= 1.0 && $dH < 2.0):
$dR = $dX; $dG = $dC; $dB = 0.0; break;
case($dH >= 2.0 && $dH < 3.0):
$dR = 0.0; $dG = $dC; $dB = $dX; break;
case($dH >= 3.0 && $dH < 4.0):
$dR = 0.0; $dG = $dX; $dB = $dC; break;
case($dH >= 4.0 && $dH < 5.0):
$dR = $dX; $dG = 0.0; $dB = $dC; break;
case($dH >= 5.0 && $dH < 6.0):
$dR = $dC; $dG = 0.0; $dB = $dX; break;
default:
$dR = 0.0; $dG = 0.0; $dB = 0.0; break;
}
$dM = $dV - $dC;
$dR += $dM; $dG += $dM; $dB += $dM;
$dR *= 255; $dG *= 255; $dB *= 255;
return array(round($dR), round($dG), round($dB));
}

Answer 6

Copied from this SO Answer by Cullub.
This code worked perfectly to convert a user email to user avatar colour. After long hours of searching, I got the correct hex value similar to the one generated using javascript on the front end.
TL;DR: The full code can be found here on Pastebin.
/**
* convert user email to hsl for user avatar
* #param string $string
* #return string HEX color code
*/
function stringToColor($string)
{
$hash = 0;
$l = 70;
$s = 60;
for ($i = 0; $i < strlen($string); $i++) {
$hash = ord($string[$i]) + (($hash << 5) - $hash);
}
$h = fmod($hash, 360);
return $this->hslToHex($h, $s, $l, true);
}
/**
* Converts HSL to Hex by converting it to
* RGB, then converting that to hex.
*
* string hslToHex($h, $s, $l[, $prependPound = true]
*
* $h is the Degrees value of the Hue
* $s is the Percentage value of the Saturation
* $l is the Percentage value of the Lightness
* $prependPound is a bool, whether you want a pound
* sign prepended. (optional - default=true)
*
* Calls:
* hslToRgb
*
* Output: Hex in the format: #00ff88 (with
* pound sign). Rounded to the nearest whole
* number.
*/
function hslToHex($h, $s, $l, $prependPound = true)
{
//convert hsl to rgb
$rgb = $this->hslToRgb($h, $s, $l);
//convert rgb to hex
$hexR = $rgb['r'];
$hexG = $rgb['g'];
$hexB = $rgb['b'];
//round to the nearest whole number
$hexR = round($hexR);
$hexG = round($hexG);
$hexB = round($hexB);
//convert to hex
$hexR = dechex($hexR);
$hexG = dechex($hexG);
$hexB = dechex($hexB);
//check for a non-two string length
//if it's 1, we can just prepend a
//0, but if it is anything else non-2,
//it must return false, as we don't
//know what format it is in.
if (strlen($hexR) != 2) {
if (strlen($hexR) == 1) {
//probably in format #0f4, etc.
$hexR = "0" . $hexR;
} else {
//unknown format
return false;
}
}
if (strlen($hexG) != 2) {
if (strlen($hexG) == 1) {
$hexG = "0" . $hexG;
} else {
return false;
}
}
if (strlen($hexB) != 2) {
if (strlen($hexB) == 1) {
$hexB = "0" . $hexB;
} else {
return false;
}
}
//if prependPound is set, will prepend a
//# sign to the beginning of the hex code.
//(default = true)
$hex = "";
if ($prependPound) {
$hex = "#";
}
$hex = $hex . $hexR . $hexG . $hexB;
return $hex;
}
/**
* Converts an HSL color value to RGB. Conversion formula
* adapted from http://www.niwa.nu/2013/05/math-behind-colorspace-conversions-rgb-hsl/.
* Assumes h, s, and l are in the format Degrees,
* Percent, Percent, and returns r, g, and b in
* the range [0 - 255].
*
* Called by hslToHex by default.
*
* Calls:
* degPercPercToHsl
* hueToRgb
*
* #param Number h The hue value
* #param Number s The saturation level
* #param Number l The luminence
* #return Array The RGB representation
*/
function hslToRgb($h, $s, $l)
{
//convert the hue's 360 degrees in a circle to 1
$h /= 360;
//convert the saturation and lightness to the 0-1
//range by multiplying by 100
$s /= 100;
$l /= 100;
//If there's no saturation, the color is a greyscale,
//so all three RGB values can be set to the lightness.
//(Hue doesn't matter, because it's grey, not color)
if ($s == 0) {
$r = $l * 255;
$g = $l * 255;
$b = $l * 255;
} else {
//calculate some temperary variables to make the
//calculation eaisier.
if ($l < 0.5) {
$temp2 = $l * (1 + $s);
} else {
$temp2 = ($l + $s) - ($s * $l);
}
$temp1 = 2 * $l - $temp2;
//run the calculated vars through hueToRgb to
//calculate the RGB value. Note that for the Red
//value, we add a third (120 degrees), to adjust
//the hue to the correct section of the circle for
//red. Simalarly, for blue, we subtract 1/3.
$r = 255 * $this->hueToRgb($temp1, $temp2, $h + (1 / 3));
$g = 255 * $this->hueToRgb($temp1, $temp2, $h);
$b = 255 * $this->hueToRgb($temp1, $temp2, $h - (1 / 3));
}
$rgb['r'] = $r;
$rgb['g'] = $g;
$rgb['b'] = $b;
return $rgb;
// return "rgb($r, $g, $b)";
}
/**
* Converts an HSL hue to it's RGB value.
*
* Input: $temp1 and $temp2 - temperary vars based on
* whether the lumanence is less than 0.5, and
* calculated using the saturation and luminence
* values.
* $hue - the hue (to be converted to an RGB
* value) For red, add 1/3 to the hue, green
* leave it alone, and blue you subtract 1/3
* from the hue.
*
* Output: One RGB value.
*
* Thanks to Easy RGB for this function (Hue_2_RGB).
* http://www.easyrgb.com/index.php?X=MATH&$h=19#text19
*
*/
function hueToRgb($temp1, $temp2, $hue)
{
if ($hue < 0) {
$hue += 1;
}
if ($hue > 1) {
$hue -= 1;
}
if ((6 * $hue) < 1) {
return ($temp1 + ($temp2 - $temp1) * 6 * $hue);
} elseif ((2 * $hue) < 1) {
return $temp2;
} elseif ((3 * $hue) < 2) {
return ($temp1 + ($temp2 - $temp1) * ((2 / 3) - $hue) * 6);
}
return $temp1;
}

Answer 7

If you have decimal RGB values (enhzflep showed how to get them), you can easily get the #ab01cd hex web string:
$rgb['r'] = ($t = round($rgb['r'] * 255, 0)) < 15 ? '0'.dechex($t) : dechex($t);
$rgb['g'] = ($t = round($rgb['g'] * 255, 0)) < 15 ? '0'.dechex($t) : dechex($t);
$rgb['b'] = ($t = round($rgb['b'] * 255, 0)) < 15 ? '0'.dechex($t) : dechex($t);
$hexweb = "#".$rgb['r'].$rgb['g'].$rgb['b'];