diff --git a/core/lib/Drupal/Core/Image/Image.php b/core/lib/Drupal/Core/Image/Image.php
index 402243f..37a4fa8 100644
--- a/core/lib/Drupal/Core/Image/Image.php
+++ b/core/lib/Drupal/Core/Image/Image.php
@@ -71,15 +71,15 @@ class Image implements ImageInterface {
   /**
    * Constructs a new Image object.
    *
-   * @param string|NULL $source
-   *   The path to an image file, or NULL to construct the object with no
-   *   image source.
+   * @param string $source
+   *   The path to an image file, or an empty string to construct the object
+   *   with no image source.
    * @param \Drupal\Core\ImageToolkit\ImageToolkitInterface $toolkit
    *   The image toolkit.
    */
   public function __construct($source, ImageToolkitInterface $toolkit) {
     $this->toolkit = $toolkit;
-    if ($source) {
+    if (!empty($source)) {
       $this->source = $source;
       $this->processInfo();
     }
diff --git a/core/lib/Drupal/Core/Image/ImageFactory.php b/core/lib/Drupal/Core/Image/ImageFactory.php
index 3bff021..a7098a0 100644
--- a/core/lib/Drupal/Core/Image/ImageFactory.php
+++ b/core/lib/Drupal/Core/Image/ImageFactory.php
@@ -36,6 +36,7 @@ class ImageFactory {
    */
   public function __construct(ImageToolkitManager $toolkit_manager) {
     $this->toolkitManager = $toolkit_manager;
+    $this->toolkitId = $this->toolkitManager->getDefaultToolkitId();
   }
 
   /**
@@ -59,43 +60,33 @@ public function setToolkitId($toolkit_id) {
    *   The ID of the image toolkit in use by the image factory.
    */
   public function getToolkitId() {
-    return $this->resolveToolkitId();
+    return $this->toolkitId;
   }
 
   /**
    * Constructs a new Image object.
    *
-   * @param string|NULL $source
-   *   The path to an image file, or NULL to construct the object with no
-   *   image source.
+   * Normally, the toolkit set as default in the admin UI is used by the
+   * factory to create new Image objects. This can be overridden through
+   * \Drupal\Core\Image\ImageInterface::setToolkitId() so that any new Image
+   * object created will use the new toolkit specified. Finally, a single
+   * Image object can be created using a specific toolkit, regardless of the
+   * current factory settings, by passing its plugin ID in the $toolkit_id
+   * argument.
+   *
+   * @param string $source
+   *   The path to an image file, or an empty string to construct the object
+   *   with no image source.
    * @param string $toolkit_id
    *   (Optional) The image toolkit ID to use for this image.
    *
    * @return \Drupal\Core\Image\ImageInterface
    *   An Image object.
+   *
+   * @see ImageFactory::setToolkitId()
    */
   public function get($source, $toolkit_id = NULL) {
-    $toolkit_id = $this->resolveToolkitId($toolkit_id);
+    $toolkit_id = $toolkit_id ?: $this->toolkitId;
     return new Image($source, $this->toolkitManager->createInstance($toolkit_id));
   }
-
-  /**
-   * Resolves a toolkit ID.
-   *
-   * @param string $toolkit_id
-   *   (Optional) An image toolkit ID. If not specified, the toolkit currently
-   *   set will be returned, or the default one if no toolkit is set.
-   *
-   * @return string
-   *   An image toolkit ID.
-   */
-  protected function resolveToolkitId($toolkit_id = NULL) {
-    if (!$toolkit_id) {
-      if (!$this->toolkitId) {
-        $this->toolkitId = $this->toolkitManager->getDefaultToolkitId();
-      }
-      $toolkit_id = $this->toolkitId;
-    }
-    return $toolkit_id;
-  }
 }