Color Brightness

color_brightness.php

<?php

function color_brightness($hex, $percent) {
    // Work out if hash given
    $hash = '';

    if (stristr($hex,'#')) {
        $hex = str_replace('#','',$hex);
        $hash = '#';
    }

    /// HEX TO RGB
    $rgb = array(hexdec(substr($hex,0,2)), hexdec(substr($hex,2,2)), hexdec(substr($hex,4,2)));
    
    //// CALCULATE
    for ($i = 0; $i < 3; $i++) {
        // See if brighter or darker
        if ($percent > 0) {
            // Lighter
            $rgb[$i] = round($rgb[$i] * $percent) + round(255 * (1-$percent));
        } else {
            // Darker
            $positivePercent = $percent - ($percent*2);
            $rgb[$i] = round($rgb[$i] * $positivePercent) + round(0 * (1-$positivePercent));
        }

        // In case rounding up causes us to go to 256
        if ($rgb[$i] > 255) {
            $rgb[$i] = 255;
        }
    }
    //// RBG to Hex
    $hex = '';

    for ($i=0; $i < 3; $i++) {
        // Convert the decimal digit to hex
        $hexDigit = dechex($rgb[$i]);

        // Add a leading zero if necessary
        if (strlen($hexDigit) == 1) {
            $hexDigit = "0" . $hexDigit;
        }

        // Append to the hex string
        $hex .= $hexDigit;
    }
    
    return $hash.$hex;
}