diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1077,30 +1077,9 @@
  *   - 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 URI's and sizes/multipliers.
  */
 function template_preprocess_image(&$variables) {
-  if (!empty($variables['uri'])) {
-    $variables['attributes']['src'] = file_create_url($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'])) {
-    $srcsets = array();
-    foreach ($variables['srcset'] as $srcset) {
-      // URI is mandatory.
-      $srcset['src'] = file_create_url($srcset['uri']);
-      $new_source = $srcset['src'];
-      if (isset($srcset['width']) && !empty($srcset['width'])) {
-        $new_source .= ' ' . $srcset['width'];
-      }
-      elseif (isset($srcset['multiplier']) && !empty($srcset['multiplier'])) {
-        $new_source .= ' ' . $srcset['multiplier'];
-      }
-      $srcsets[] = $new_source;
-    }
-    $variables['attributes']['srcset'] = implode(', ', $srcsets);
-  }
+  $variables['attributes']['src'] = file_create_url($variables['uri']);
  
   foreach (array('width', 'height', 'alt', 'title') as $key) {
     if (isset($variables[$key])) {
@@ -1141,9 +1120,29 @@
  *   - title: The title text is displayed when the image is hovered in some
  *     popular browsers.
  *   - attributes: Associative array of attributes to be placed in the img tag.
+ *   - srcset: Array of multiple URI's and sizes/multipliers.
  */
 function template_preprocess_image(&$variables) {
-  $variables['attributes']['src'] = file_create_url($variables['uri']);
+  if (!empty($variables['uri'])) {
+    $variables['attributes']['src'] = file_create_url($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.
+      $source = file_create_url($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') as $key) {
     if (isset($variables[$key])) {
@@ -2308,7 +2307,7 @@
       // - http://dev.w3.org/html5/spec/Overview.html#alt
       // The title attribute is optional in all cases, so it is omitted by
       // default.
-      'variables' => array('uri' => NULL, 'width' => NULL, 'height' => NULL, 'alt' => '', 'title' => NULL, 'attributes' => array()),
+      'variables' => array('uri' => NULL, 'width' => NULL, 'height' => NULL, 'alt' => '', 'title' => NULL, 'attributes' => array(), 'srcset' => array()),
       'template' => 'image',
     ),
     'breadcrumb' => array(
@@ -2400,7 +2399,7 @@
       // - http://dev.w3.org/html5/spec/Overview.html#alt
       // The title attribute is optional in all cases, so it is omitted by
       // default.
-      'variables' => array('uri' => NULL, 'width' => NULL, 'height' => NULL, 'alt' => '', 'title' => NULL, 'attributes' => array(), 'srcset' => array()),
+      'variables' => array('uri' => NULL, 'width' => NULL, 'height' => NULL, 'alt' => '', 'title' => NULL, 'attributes' => array()),
       'template' => 'image',
     ),
     'breadcrumb' => array(
diff -u b/core/modules/image/src/ImageEffectInterface.php b/core/modules/image/src/ImageEffectInterface.php
--- b/core/modules/image/src/ImageEffectInterface.php
+++ b/core/modules/image/src/ImageEffectInterface.php
@@ -47,7 +47,7 @@
    * Determines the MIME type of the image effect.
    *
    * @param string $mime_type
-   *   MIME type to be modified.
+   *   The MIME type to be modified.
    */
   public function transformMimeType(&$mime_type);
  
diff -u b/core/modules/image/src/ImageStyleInterface.php b/core/modules/image/src/ImageStyleInterface.php
--- b/core/modules/image/src/ImageStyleInterface.php
+++ b/core/modules/image/src/ImageStyleInterface.php
@@ -134,7 +134,7 @@
    * Determines the MIME type of the image style.
    *
    * @param string $mime_type
-   *   MIME type to be modified.
+   *   The MIME type to be modified.
    */
   public function transformMimeType(&$mime_type);