/**
* Compares the histogram object against another histogram object.
* The lower the returned value is, the closer a match they are.
*
* @param Histogram $histogram The histogram object to compare against.
* @return int The comparison value. Lower means a closer match.
*/
private function compare_against($histogram)
{
$value = 0;
// If there is no histogram (image couldn't be analyzed), never match anything
if ($this->histogram == '' || $histogram == '') {
return self::$match_threshold;
}
foreach ($this->histogram as $channel_key => $color_channel) {
foreach ($color_channel as $bucket_key => $color_bucket) {
$value += abs($color_bucket - $histogram->get($channel_key, $bucket_key));
// Stop computing early if the value will never be a match
if ($value >= self::$match_threshold) {
return self::$match_threshold;
}
}
}
return $value;
}
