Is there an easy way to get the image derivatives links?

I'm working with complex image styles, and I'd like to be able to load all the different derivatives quickly to check they're being processed correctly.

But I don't see how to easily get the links. The best I can come up with is opening the node in JSONAPI and, with the patch from https://www.drupal.org/project/drupal/issues/2825812, getting the URLs for derivatives from that.

It there something easier?

Back in the Drupal 6 days, the Image module showed the links to all the sizes on the image node itself.

You can get that info with the following code:

$original_uri = 'public://images/image.jpg';

$styles = \Drupal::entityTypeManager()->getStorage('image_style')->loadMultiple();

$urls = array_map(function($style) use ($original_uri) {
  return $style->buildUri($original_uri);
}, $styles);

$urls should now contain a list of URLs based on the original, one for each image style in the system.

To get the image derivative URI for an image to which is applied a specific image style, you can use the following code.

// Load the ImageStyle instance in $image_style, for example with
// $image_style = ImageStyle::load($id).
// $image_uri is the path/URI for the image to which the style is applied. 
if ($image_style->supportsUri($image_uri)) {
  $derivative_uri = $style->buildUri($image_uri);
}

Keep in mind that image derivatives are created only when the URL returned from $image_style->buildURL($image_uri) is requested (from a browser). Building the URI (or the URL) doesn't generate the derivative image; it returns the URI (URL) for an image that couldn't exist, yet.

To check an image derivative could be created, code similar to the one used from ImageStyleDownloadController::deliver() should be used.

if ($image_style->supportsUri($image_uri)) {
  $derivative_uri = $style->buildUri($image_uri);

  if (!file_exists($image_uri)) {
    $path_info = pathinfo($image_uri);
    $converted_image_uri = $path_info['dirname'] . DIRECTORY_SEPARATOR . $path_info['filename'];
    if (file_exists($converted_image_uri)) {
      $image_uri = $converted_image_uri;
    }
  }

  $success = file_exists($derivative_uri) || $image_style->createDerivative($image_uri, $derivative_uri);

  if ($success) {
    $image = Drupal::service('image.factory')->get($derivative_uri);
    $uri = $image->getSource();
  }
}