How can I convert a binary string from a form to a file in Symfony2?

Question

I have a REST api, and I'm submitting GIF files to it basically. It's returning a 400 error though.

This is the code that handles the conversion at the minute.

        $imgstr = $params['file'];

        $dataObject = str_replace("data:image/gif;base64,", "", $imgstr);

        $file = base64_decode($dataObject);

        $entity->setDescription($params['description']);
        $entity->setFile($dataObject);
        $entity->setUser($user);

        $em->persist($entity);
        $em->flush();

The setFile() method expects a Symfony\Component\HttpFoundation\File\UploadedFile object. It works with normal form submissions from the web front-end, just not the app.

It does pick up the binary string with the mime type prepended etc. But it won't store it.

Cheers