src/ImageFileCache/Manager.php
public function matchUri($uri)
    {
        $pattern = '#^' . preg_quote($this->options->getUriPath(), '#') . '/[0-9a-z]/[0-9a-z]/([0-9a-z]+)\.[a-zA-Z]{3,4}$#';
        $matches = [];
        preg_match($pattern, $uri, $matches);
        
        return isset($matches[1]) ? $matches[1] : null;
    }
public function matchUri($uri)
    {
        $pattern = '#^' . preg_quote($this->options->getUriPath(), '#') . '/[0-9a-z]/[0-9a-z]/([0-9a-z]+)\.[a-zA-Z]{3,4}$#';
        $matches = [];
        preg_match($pattern, $uri, $matches);
        
        return isset($matches[1]) ? $matches[1] : null;
    }
Match the passed $uri and return an image ID on success

@param string $uri
@return null|string Image ID