move_file.drush

#!/usr/bin/env drush

/**
 * Usage: drush move_file.drush
 */

use Drupal\file\Entity\File;

drush_print('Ready to move private image files...');
$confirm = drush_confirm('Do you want to move all managed private image files to public files?');

// Stop if confirmation step failed.
if (!$confirm) {
  drush_set_context('DRUSH_EXECUTION_COMPLETED', TRUE);
  drush_set_context('DRUSH_EXIT_CODE', DRUSH_SUCCESS);
  exit(0);
}

// Select all private image files.
$file_ids = \Drupal::database()->select('file_managed', 'f')
  ->fields('f', ['fid'])
  ->condition('f.uri', 'private://%', 'LIKE')
  ->condition('f.filemime', 'image%', 'LIKE')
  ->execute()->fetchCol();

// Exit if we have nothing to do.
if (empty($file_ids)) {
  drush_print('Nothing to do...');
  drush_set_context('DRUSH_EXECUTION_COMPLETED', TRUE);
  drush_set_context('DRUSH_EXIT_CODE', DRUSH_SUCCESS);
  exit(0);
}

$time_start = microtime(true);
$chunks = array_chunk($file_ids, 50);

// Process the file chunks.
foreach ($chunks as $chunk) {
  process_files($chunk);
}

$time_end = microtime(true);
$execution_time = ($time_end - $time_start);
drush_print('Finished processing ' . count($file_ids) . ' files...');
drush_print('Total Execution Time: ' . round($execution_time, 2) . ' seconds');

drush_print('You may consider clearing the cache now.');

/**
 * Process files.
 */
function process_files($file_ids) {
  drush_print('Starting to process files...');

  $i = 0;
  $total = count($file_ids);
  $files = File::loadMultiple($file_ids);

  // Loop through the files.
  foreach ($files as $file) {
    // Loop through the results and move them to the public folder.
    $destination = $file->getFileUri();

    // Change the destination and move the file.
    $destination = str_replace('private', 'public', $destination);
    if (file_prepare_directory($destination, FILE_CREATE_DIRECTORY)) {
      file_move($file, $destination);
    }

    drush_print('Processed file with ID ' . $file->id() . ' (' . ($i + 1) . '/' . $total . ')');
    $i++;
  }

  drush_print('Processed ' . $i . ' files...');
}