function image_style_deliver

Menu callback; Given a style and image path, generate a derivative.

After generating an image, transfer it to the requesting agent.

Parameters

$style: The image style

File

drupal/core/modules/image/image.module, line 653

Exposes global functionality for creating image styles.

Code

function image_style_deliver($style, $scheme) {

  // Check that the style is defined and the scheme is valid.
  if (!$style || !file_stream_wrapper_valid_scheme($scheme)) {
    drupal_exit();
  }
  $args = func_get_args();
  array_shift($args);
  array_shift($args);
  $target = implode('/', $args);
  $image_uri = $scheme . '://' . $target;
  $derivative_uri = image_style_path($style
    ->id(), $image_uri);

  // If using the private scheme, let other modules provide headers and
  // control access to the file.
  if ($scheme == 'private') {
    if (file_exists($derivative_uri)) {
      file_download($scheme, file_uri_target($derivative_uri));
    }
    else {
      $headers = module_invoke_all('file_download', $image_uri);
      if (in_array(-1, $headers) || empty($headers)) {
        throw new AccessDeniedHttpException();
      }
      if (count($headers)) {
        foreach ($headers as $name => $value) {
          drupal_add_http_header($name, $value);
        }
      }
    }
  }

  // Don't try to generate file if source is missing.
  if (!file_exists($image_uri)) {
    watchdog('image', 'Unable to generate the derived image from image at %path.', array(
      '%path' => $derivative_uri,
    ));
    return new Response(t('Error generating image, missing source file.'), 404);
  }

  // Don't start generating the image if the derivative already exists or if
  // generation is in progress in another thread.
  $lock_name = 'image_style_deliver:' . $style
    ->id() . ':' . drupal_hash_base64($image_uri);
  if (!file_exists($derivative_uri)) {
    $lock_acquired = lock()
      ->acquire($lock_name);
    if (!$lock_acquired) {

      // Tell client to retry again in 3 seconds. Currently no browsers are known
      // to support Retry-After.
      drupal_add_http_header('Status', '503 Service Unavailable');
      drupal_add_http_header('Retry-After', 3);
      print t('Image generation in progress. Try again shortly.');
      drupal_exit();
    }
  }

  // Try to generate the image, unless another thread just did it while we were
  // acquiring the lock.
  $success = file_exists($derivative_uri) || image_style_create_derivative($style, $image_uri, $derivative_uri);
  if (!empty($lock_acquired)) {
    lock()
      ->release($lock_name);
  }
  if ($success) {
    $image = image_load($derivative_uri);
    $uri = $image->source;
    $headers = array(
      'Content-Type' => $image->info['mime_type'],
      'Content-Length' => $image->info['file_size'],
    );
    return file_transfer($uri, $headers);
  }
  else {
    watchdog('image', 'Unable to generate the derived image located at %path.', array(
      '%path' => $derivative_uri,
    ));
    return new Response(t('Error generating image.'), 500);
  }
}