/**
* Increases or decreases the brightness of a color by a percentage of the current brightness.
*
* @param string $hexCode Supported formats: `#FFF`, `#FFFFFF`, `FFF`, `FFFFFF`
* @param float $adjustPercent A number between -1 and 1. E.g. 0.3 = 30% lighter; -0.4 = 40% darker.
*
* @return string
*
* @author maliayas
*/
function adjustBrightness($hexCode, $adjustPercent) {
$hexCode = ltrim($hexCode, '#');
if (strlen($hexCode) == 3) {
$hexCode = $hexCode[0] . $hexCode[0] . $hexCode[1] . $hexCode[1] . $hexCode[2] . $hexCode[2];
}
$hexCode = array_map('hexdec', str_split($hexCode, 2));
foreach ($hexCode as & $color) {
$adjustableLimit = $adjustPercent < 0 ? $color : 255 - $color;
$adjustAmount = ceil($adjustableLimit * $adjustPercent);
$color = str_pad(dechex($color + $adjustAmount), 2, '0', STR_PAD_LEFT);
}
return '#' . implode($hexCode);
}