flush derivatives for single file

Here's a function I wrote to flush all derivative images for a given file. I call it from the ImageField module when deleting an image, so that I don't get left with unneeded derivatives.

/**
 * Flush cached media only for given file
 * @param file
 *   The file for which to flush cached media
 */
function _imagecache_file_flush($file) {
  $presets = _imagecache_get_presets();

  foreach ($presets as $preset) {
    $filepath = imagecache_create_path($preset, $file['filepath']);

    if (is_file($filepath)) {
      @unlink($filepath);

      // Remove all empty parent directories.
      $patharray = explode("/", dirname($filepath));
      $pathlength = count($patharray);
      $foundfiles = false;
      // Remember that we never want the leading "files" dir to be deleted!
      for ($i = $pathlength; !$foundfiles && $i > 1; $i--) {
        $currentdir = implode("/", array_slice($patharray, 0, $i));
        $filesindir = glob($currentdir. "/*");
        if (count($filesindir) == 0) {
          @rmdir($currentdir);
        } else {
          $foundfiles = true;
        }
      }
    }
  }

  drupal_set_message(t('Flushed Preset Images for file: @file',
                     array('@file' => $file['filepath'])));
}

In ImageField, wherever the line file_delete($file['filepath']); occurs, I've inserted the following above:

if (function_exists(_imagecache_file_flush)) {
  _imagecache_file_flush($file);
}

I do apologise for not providing a patch. Just thought I'd share my code.