Upload obrazka z url

Witam,

Nie mogę nigdzie znaleźć odpowiedzi, jak w Symfony2 zrobić upload obrazka z url. Mam upload obrazka zwykły, który działa bez zarzutu. Jak dorobić do tego upload z URL?

Formularz:

->add('title', TextType::class, array(
                'label' => 'Tytuł',
                'attr' => array(
                    'placeholder' => 'Tytuł'
                )
            ))
            ->add('pictureFile', FileType::class, array(
                'label' => 'Obrazek'
            ))

Encja:

/**
     * Get picture
     *
     * @return string 
     */
    public function getPicture() {
        return Pic::UPLOAD_DIR . $this->picture;
    }

    public function getPictureFile() {
        return $this->pictureFile;
    }

    public function setPictureFile(UploadedFile $pictureFile) {
        $this->pictureFile = $pictureFile;
        $this->updateDate = new \DateTime();
        return $this;
    }

 /**
     * @ORM\PostPersist
     * @ORM\PostUpdate
     */
    public function postSave() {
        if (NULL !== $this->getPictureFile()) {
            $this->getPictureFile()->move($this->getUploadRootDir(), $this->picture);
            unset($this->pictureFile);

            if (isset($this->pictureTemp)) {
                unlink($this->getUploadRootDir() . '/' . $this->pictureTemp);
                unset($this->pictureTemp);
            }
        }
    }