Annotations Convert and ConvertMultiple

[jonny-no1]

As previously brought up, please consider my implementation attempt of the Convert annotation

// ...
use Snowcap\ImBundle\Doctrine\Mapping as SnowcapIm;
// ...

  /**
   *
   * @Assert\File(maxSize="6000000")
   * @SnowcapIm\Convert(params={"thumbnail"="100x100>"}, targetProperty="thumbnail")
   */
  public $file;

  public $thumbnail;

as well as the ConvertMultiple annotation

// ...
use Snowcap\ImBundle\Doctrine\Mapping as SnowcapIm;
// ...

  /**
   *
   * @Assert\File(maxSize="6000000")
   * @SnowcapIm\Mogrify(params={"resize"="1024"})
   * @SnowcapIm\ConvertMultiple({
   *     @SnowcapIm\Convert(params={"resize"="612"}, targetProperty="medium"),
   *     @SnowcapIm\Convert(params={"thumbnail"="100x100>"}, targetProperty="thumbnail")
   * })
   */
  public $file;

  public $medium;

  public $thumbnail;

I am almost there, but I am struggling in the last step because the convert method of the Manager class only allows paths relative to the web root for the input file. I am currently uncertain as to a good solution to this problem and would be thankful for any suggestions.