function color_inverse($color){
$color = str_replace('#', '', $color);
if (strlen($color) != 6){ return '000000'; }
$rgb = '';
for ($x=0;$x<3;$x++){
$c = 255 - hexdec(substr($color,(2*$x),2));
$c = ($c < 0) ? 0 : dechex($c);
$rgb .= (strlen($c) < 2) ? '0'.$c : $c;
}
return '#'.$rgb;
}