Question

I am working on a dynamic store project and I use a loop to print all color options for a product as color boxes, however I really need to add a “border” to these colors which are light. I tried something like the following but It is very limited, it is actually limited to white color only, it won’t catch something like #ddd, #eea… etc

Here is my loop:

foreach($colors as $color) {
    $color = trim($color);
    if (!empty($color)) {
        if (in_array($color, array('white','White','#fff','#FFF','#FFFFFF','#ffffff'))) {
            $bordercolor = '#bbb';
        } else {
            $bordercolor = $color;
        }
    }
}

Colors is an array from backend like: White, #000, #cc0000, etc. It is not practical to add all exceptions in the if/else condition too, any quick idea?

Answer 1

Transform HTML colour to RGB, then to Hue-Saturation-Lightnes (HSV)

<?php

function HTMLToRGB($htmlCode)
  {
    if($htmlCode[0] == '#')
      $htmlCode = substr($htmlCode, 1);

    if (strlen($htmlCode) == 3)
    {
      $htmlCode = $htmlCode[0] . $htmlCode[0] . $htmlCode[1] . $htmlCode[1] . $htmlCode[2] . $htmlCode[2];
    }

    $r = hexdec($htmlCode[0] . $htmlCode[1]);
    $g = hexdec($htmlCode[2] . $htmlCode[3]);
    $b = hexdec($htmlCode[4] . $htmlCode[5]);

    return $b + ($g << 0x8) + ($r << 0x10);
  }

function RGBToHSL($RGB) {
    $r = 0xFF & ($RGB >> 0x10);
    $g = 0xFF & ($RGB >> 0x8);
    $b = 0xFF & $RGB;

    $r = ((float)$r) / 255.0;
    $g = ((float)$g) / 255.0;
    $b = ((float)$b) / 255.0;

    $maxC = max($r, $g, $b);
    $minC = min($r, $g, $b);

    $l = ($maxC + $minC) / 2.0;

    if($maxC == $minC)
    {
      $s = 0;
      $h = 0;
    }
    else
    {
      if($l < .5)
      {
        $s = ($maxC - $minC) / ($maxC + $minC);
      }
      else
      {
        $s = ($maxC - $minC) / (2.0 - $maxC - $minC);
      }
      if($r == $maxC)
        $h = ($g - $b) / ($maxC - $minC);
      if($g == $maxC)
        $h = 2.0 + ($b - $r) / ($maxC - $minC);
      if($b == $maxC)
        $h = 4.0 + ($r - $g) / ($maxC - $minC);

      $h = $h / 6.0; 
    }

    $h = (int)round(255.0 * $h);
    $s = (int)round(255.0 * $s);
    $l = (int)round(255.0 * $l);

    return (object) Array('hue' => $h, 'saturation' => $s, 'lightness' => $l);
  }

$colour = '#F12346';
$rgb = HTMLToRGB($colour);
$hsl = RGBToHSL($rgb);

var_dump($hsl);

Usage:

$colour = '#F12346';
$rgb = HTMLToRGB($colour);
$hsl = RGBToHSL($rgb);
if($hsl->lightness > 200) {
  // this is light colour!
}

Source:

• http://www.caperna.org/computing/repository/hsl-rgb-color-conversion-php

Demo:

• http://codepad.org/X7KV4n4n