Simple twig extension function that returns datauri string for given file

DataUriExtension.php

<?php

namespace AppBundle\Twig\Extension;

use Symfony\Component\HttpFoundation\File\File;
use Symfony\Component\HttpKernel\KernelInterface;

/**
 * Usage example,
 *  <img src="{{ data_uri('@AcmeBundle/Resources/public/images/logo.svg') }}">
 */
class DataUriExtension extends \Twig_Extension
{
    /** @var KernelInterface */
    protected $kernel;

    public function __construct(KernelInterface $kernel) {
        $this->kernel = $kernel;
    }

    /**
     * Returns the name of the extension.
     *
     * @return string The extension name
     */
    public function getName() {
        return 'base64';
    }

    /**
     * {@inheritdoc}
     */
    public function getFunctions() {
        return [
            new \Twig_SimpleFunction('data_uri', [$this, 'getDataUri'])
        ];
    }

    public function getDataUri($path) {
        $realpath = $this->kernel->locateResource($path);
        $file = new File($realpath, true);
        $mimeType = $file->getMimeType();
        $params = [];
        $data = file_get_contents($realpath);
        $isBinaryData = strpos($mimeType, 'text/') !== 0;

        if (null === $mimeType) {
            $mimeType = 'text/plain';
            $parameters['charset'] = 'US-ASCII';
        }

        $parameters = '';
        if (0 !== count($params)) {
            foreach ($params as $paramName => $paramValue) {
                $parameters .= sprintf(';%s=%s', $paramName, $paramValue);
            }
        }

        $base64 = '';
        if ($isBinaryData) {
            $base64 = sprintf(';%s', 'base64');
            $dataURI = base64_encode($data);
        } else {
            $dataURI = rawurlencode($data);
        }

        return sprintf('data:%s%s%s,%s', $mimeType, $parameters, $base64, $dataURI);
    }
}

services.yml

services:
  app_datauri.twig_extension:
      class: AppBundle\Twig\Extension\DataUriExtension
      public: false
      arguments: ["@kernel"]
      tags:
          - { name: twig.extension }