A drupal 8 controller function to handle photo upload requests.

Drupal 8 upload photo controller

public function uploadPhoto(Profile $profile, Request $request) {

    if ($request->getMethod() === 'POST' || $request->getMethod() === 'PUT') {

      // Decode body
      $body_raw = $request->getContent();
      $body = json_decode($body_raw);

      $imageName = $body->name;
      $imageData = base64_decode(preg_replace('#^data:image/\w+;base64,#i', '', $body->data));
      \Drupal::logger('uploadPhoto')->notice('$imageName: %imageName, $imageData: %imageData', ['%imageName' => $imageName, '%imageData' => $imageData]);

      $directory = $this->ensureProfileImageDirectory();
      $destination = $directory . $imageName;
      $saved_file = file_save_data($imageData, $destination);
      \Drupal::logger('uploadPhoto')->notice('$directory: %directory, $destination: %destination, $saved_path: %saved_path', [
        '%directory' => $directory,
        '%destination' => $destination,
        '%saved_path' => $saved_file->getFileUri(),
      ]);

      $file_usage = \Drupal::service('file.usage');
      $file_usage->add($saved_file, 'onboarding', 'profile', $profile->id());

      $profile->field_profile_image = $saved_file;
      $profile->save();

        // Doesn't work with multi-part requests from react, not sure why.
//      $validators = [
//        'file_validate_extensions' => ['jpg jpeg gif png'],
//      ];
//      if (!$file = file_save_upload('photo', $validators, FALSE, $delta = 0)){
//        \Drupal::logger('file')->notice('The photo upload failed for profile id %profile_id', ['%profile_id' => $profile->id()]);
//
//        return JsonResponse::create(['errorMessage' => 'The photo could not be saved.'], 500);
//      }
//      \Drupal::logger('file')->notice('The photo uploaded as %file_id', ['%file_id' => $file->id()]);

      $body = [
        'success' => 1,
        'file_id' => $saved_file->id(),
        'file_uri' => $saved_file->getFileUri(),
        'file_url' => $saved_file->url(),
      ];
      return JsonResponse::create($body);
    }

    if ($request->getMethod() === 'GET') {

      return JsonResponse::create(['errorMessage' => 'Use post request to upload photo to profile %profile.', ['%profile' => $profile->id()]], 400);
    }

    return JsonResponse::create(['errorMessage' => 'This call only accepts post requests.'], 400);
  }