问题
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 :)
回答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
回答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, $b)";
}
回答3:
The PEAR package Image_Color2 has methods to transform between color models - see convertTo.
回答4:
My tests of all other implementations showed only weird and possibly unplausible results. Here is a PHP implementation of @Mohsen's code from https://stackoverflow.com/a/9493060/1598477. Plus a test to show the full beauty...
Sorry to cross-post this. But I really haven't seen any other implementation that gives the quality I needed.
/**
* Converts an HSL color value to RGB. Conversion formula
* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
* Assumes h, s, and l are contained in the set [0, 1] and
* returns r, g, and b in the set [0, 255].
*
* @param {number} h The hue
* @param {number} s The saturation
* @param {number} l The lightness
* @return {Array} The RGB representation
*/
function hue2rgb($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 */
回答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));
}
回答6:
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'];
来源：https://stackoverflow.com/questions/20423641/php-function-to-convert-hsl-to-rgb-or-hex