core/themes/stable/stable.theme                    | 64 ++++++++++++++++++++++
 core/themes/stable/templates/field/image.html.twig |  1 -
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/core/themes/stable/stable.theme b/core/themes/stable/stable.theme
index 456a4ad..b927056 100644
--- a/core/themes/stable/stable.theme
+++ b/core/themes/stable/stable.theme
@@ -23,3 +23,67 @@ function stable_preprocess_links(&$variables) {
     }
   }
 }
+
+
+/**
+ * Prepares variables for image templates.
+ *
+ * Default template: image.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - uri: Either the path of the image file (relative to base_path()) or a
+ *     full URL.
+ *   - width: The width of the image (if known).
+ *   - height: The height of the image (if known).
+ *   - alt: The alternative text for text-based browsers. HTML 4 and XHTML 1.0
+ *     always require an alt attribute. The HTML 5 draft allows the alt
+ *     attribute to be omitted in some cases. Therefore, this variable defaults
+ *     to an empty string, but can be set to NULL for the attribute to be
+ *     omitted. Usually, neither omission nor an empty string satisfies
+ *     accessibility requirements, so it is strongly encouraged for code
+ *     building variables for image.html.twig templates to pass a meaningful
+ *     value for this variable.
+ *     - http://www.w3.org/TR/REC-html40/struct/objects.html#h-13.8
+ *     - http://www.w3.org/TR/xhtml1/dtds.html
+ *     - http://dev.w3.org/html5/spec/Overview.html#alt
+ *   - title: The title text is displayed when the image is hovered in some
+ *     popular browsers.
+ *   - attributes: Associative array of attributes to be placed in the img tag.
+ *   - srcset: Array of multiple URIs and sizes/multipliers.
+ *   - sizes: The sizes attribute for viewport-based selection of images.
+ *     - http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content.html#introduction-3:viewport-based-selection-2
+ */
+function stable_preprocess_image(&$variables) {
+  if (!empty($variables['uri'])) {
+    $variables['attributes']['src'] = file_url_transform_relative(file_create_url($variables['uri']));
+  }
+  // Generate a srcset attribute conforming to the spec at
+  // http://www.w3.org/html/wg/drafts/html/master/embedded-content.html#attr-img-srcset
+  if (!empty($variables['srcset'])) {
+    $srcset = array();
+    foreach ($variables['srcset'] as $src) {
+      // URI is mandatory.
+      $source = file_url_transform_relative(file_create_url($src['uri']));
+      if (isset($src['width']) && !empty($src['width'])) {
+        $source .= ' ' . $src['width'];
+      }
+      elseif (isset($src['multiplier']) && !empty($src['multiplier'])) {
+        $source .= ' ' . $src['multiplier'];
+      }
+      $srcset[] = $source;
+    }
+    $variables['attributes']['srcset'] = implode(', ', $srcset);
+  }
+
+  foreach (array('width', 'height', 'alt', 'title', 'sizes') as $key) {
+    if (isset($variables[$key])) {
+      // If the property has already been defined in the attributes,
+      // do not override, including NULL.
+      if (array_key_exists($key, $variables['attributes'])) {
+        continue;
+      }
+      $variables['attributes'][$key] = $variables[$key];
+    }
+  }
+}
diff --git a/core/themes/stable/templates/field/image.html.twig b/core/themes/stable/templates/field/image.html.twig
index 71f1e20..484268d 100644
--- a/core/themes/stable/templates/field/image.html.twig
+++ b/core/themes/stable/templates/field/image.html.twig
@@ -1,4 +1,3 @@
-{% extends "@system/image.html.twig" %}
 {#
 /**
  * @file