public function contrastColors($backgroundColor)
{
$background = Color::stringToRgb24($backgroundColor);
$this->string = preg_replace_callback('/(?<!\\$)((?:\\$[\\$])*)(\\$[0-9a-f][^\\$]{0,2})/iu', function ($matches) use($background) {
$color = Color::stringToRgb24($matches[2]);
$color = Color::contrast($color, $background);
$color = Color::rgb24ToRgb12($color);
$color = Color::rgb12ToString($color);
return $matches[1] . '$' . $color;
}, $this->string);
return $this;
}
