Find Appropriate Colour In PHP

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25th February 2009 - 2 minutes read time

Use the following function if you want to print the text in a particular colour, depending on what the background colour is.

function opposite($color) {
  $white = 0;
  for ($i = 0; $i &lt; 6; $i += 2) {
    $white += base_convert(substr($color,$i,2),16,10) < 127 ? 1 : 0;
  }
  return $white <= 2 ? "000000" : "ffffff";
}

It works by looking at the colour and seeing how much of it is white. If greater than two parts are significantly white then the color returned is black, otherwise white is returned.

Here are some examples to test the function out.

echo '<span style="background-color:#ffffff;color:#'.opposite('ffffff').'">XXXXXX</span>';
echo '<span style="background-color:#000000;color:#'.opposite('000000').'">XXXXXX</span>';
echo '<span style="background-color:#fedbad;color:#'.opposite('fedbad').'">XXXXXX</span>';
echo '<span style="background-color:#123456;color:#'.opposite('123456').'">XXXXXX</span>';
echo '<span style="background-color:#fe13ef;color:#'.opposite('fe13ef').'">XXXXXX</span>';

PHP