thara Posted July 13, 2020 Share Posted July 13, 2020 I am trying to convert colors from Hex to HSL (Not HSL to Hex). I am using a PHP function for this purpose. But It's not working properly for some colors. For example for #e04c4c the HSL should be (0, 70%, 59%) which it isn't the case with the function. function hexToHsl($hex) { $red = hexdec(substr($hex, 0, 2)) / 255; $green = hexdec(substr($hex, 2, 2)) / 255; $blue = hexdec(substr($hex, 4, 2)) / 255; $cmin = min($red, $green, $blue); $cmax = max($red, $green, $blue); $delta = $cmax - $cmin; if ($delta === 0) { $hue = 0; } elseif ($cmax === $red) { $hue = (($green - $blue) / $delta) % 6; } elseif ($cmax === $green) { $hue = ($blue - $red) / $delta + 2; } else { $hue = ($red - $green) / $delta + 4; } $hue = round($hue * 60); if ($hue < 0) { $hue += 360; } $lightness = (($cmax + $cmin) / 2) * 100; $saturation = $delta === 0 ? 0 : ($delta / (1 - abs(2 * $lightness - 1))) * 100; if ($saturation < 0) { $saturation += 100; } $lightness = round($lightness); $saturation = round($saturation); //return "hsl(${hue}, ${saturation}%, ${lightness}%)"; return array($hue, $saturation, $lightness); } This is how I used it: $templatePrimaryColor = '#e04c4c'; $templatePrimaryColor = str_replace("#", "",$templatePrimaryColor); list($h,$s,$l) = hexToHsl($templatePrimaryColor); $primaryColor = "hsl(${h}, ${s}%, ${l}%)"; This is the output: echo '<pre>',print_r(hexToHsl($templatePrimaryColor)).'</pre>'; Array ( [0] => 0 [1] => 99 [2] => 59 ) 1 Does anyone know what is the problem there? Thank you. Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/ Share on other sites More sharing options...
requinix Posted July 13, 2020 Share Posted July 13, 2020 $lightness = (($cmax + $cmin) / 2) * 100; $saturation = $delta === 0 ? 0 : ($delta / (1 - abs(2 * $lightness - 1))) * 100; You're multiplying the lightness by 100 too early. This throws off the saturation calculation. Leave it as $cmax+$cmin/2 and multiply when you do the round() later. Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579585 Share on other sites More sharing options...
Barand Posted July 13, 2020 Share Posted July 13, 2020 Your method has a fatal problem with greys (ie when R = G = B) Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579588 Share on other sites More sharing options...
requinix Posted July 13, 2020 Share Posted July 13, 2020 24 minutes ago, Barand said: Your method has a fatal problem with greys (ie when R = G = B) You mean when $delta === 0? Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579589 Share on other sites More sharing options...
Barand Posted July 13, 2020 Share Posted July 13, 2020 Yes, if all 3 components are equal then $delta is zero, giving a division by zero error. Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579592 Share on other sites More sharing options...
requinix Posted July 13, 2020 Share Posted July 13, 2020 In the $hue calculations? The first branch handles the $delta=0 case. Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579593 Share on other sites More sharing options...
Barand Posted July 13, 2020 Share Posted July 13, 2020 $templatePrimaryColor = '555555'; echo '<pre>',print_r(hexToHsl($templatePrimaryColor)).'</pre>'; -> Warning: Division by zero in C:\inetpub\wwwroot\test\winuser\noname3.php on line 14 Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579594 Share on other sites More sharing options...
Barand Posted July 13, 2020 Share Posted July 13, 2020 43 minutes ago, requinix said: The first branch handles the $delta=0 case. Not quite. var_dump($delta) gives float(0), therefore the first branch needs to be either if ($delta === 0.0) { or if ($delta == 0) { 1 Quote Link to comment https://forums.phpfreaks.com/topic/311078-php-function-to-convert-hex-to-hsl-not-hsl-to-hex/#findComment-1579595 Share on other sites More sharing options...
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