diff --git a/core/lib/Drupal/Core/Image/Image.php b/core/lib/Drupal/Core/Image/Image.php
index f7a5cd7..6b56ccc 100644
--- a/core/lib/Drupal/Core/Image/Image.php
+++ b/core/lib/Drupal/Core/Image/Image.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Image;
 
+use Drupal\Component\Utility\Unicode;
 use Drupal\Core\ImageToolkit\ImageToolkitInterface;
 
 /**
@@ -48,13 +49,6 @@ class Image implements ImageInterface {
   protected $width = 0;
 
   /**
-   * Commonly used file extension for the image.
-   *
-   * @var string
-   */
-  protected $extension = '';
-
-  /**
    * Image type represented by a PHP IMAGETYPE_* constant (e.g. IMAGETYPE_JPEG).
    *
    * @var int
@@ -62,13 +56,6 @@ class Image implements ImageInterface {
   protected $type;
 
   /**
-   * MIME type (e.g. 'image/jpeg', 'image/gif', 'image/png').
-   *
-   * @var string
-   */
-  protected $mimeType = '';
-
-  /**
    * File size in bytes.
    *
    * @var int
@@ -113,9 +100,9 @@ public function isExisting() {
   /**
    * {@inheritdoc}
    */
-  public function getExtension() {
+  public function getDefaultExtension() {
     $this->processInfo();
-    return $this->extension;
+    return Unicode::strtolower(image_type_to_extension($this->type, FALSE));
   }
 
   /**
@@ -171,7 +158,7 @@ public function getType() {
    */
   public function getMimeType() {
     $this->processInfo();
-    return $this->mimeType;
+    return image_type_to_mime_type($this->type);
   }
 
   /**
@@ -250,15 +237,7 @@ protected function processInfo() {
       $this->height = $details['height'];
       $this->width = $details['width'];
       $this->type = $details['type'];
-      $this->mimeType = $details['mime_type'];
       $this->fileSize = filesize($destination);
-      $this->extension = pathinfo($destination, PATHINFO_EXTENSION);
-
-      // It may be a temporary file, without extension, or an image created from
-      // an image resource. Fallback to default extension for this image type.
-      if (empty($this->extension)) {
-        $this->extension = image_type_to_extension($this->type, FALSE);
-      }
 
       $this->processed = TRUE;
     }
diff --git a/core/lib/Drupal/Core/Image/ImageInterface.php b/core/lib/Drupal/Core/Image/ImageInterface.php
index 151bef1..59f3be8 100644
--- a/core/lib/Drupal/Core/Image/ImageInterface.php
+++ b/core/lib/Drupal/Core/Image/ImageInterface.php
@@ -29,12 +29,12 @@ public function isSupported();
   public function isExisting();
 
   /**
-   * Returns the extension of the image file.
+   * Returns the default file extension of the image, based on its type.
    *
    * @return string
-   *   The extension of the file, or an empty string if the file is invalid.
+   *   The default file extension of the image.
    */
-  public function getExtension();
+  public function getDefaultExtension();
 
   /**
    * Returns the height of the image file.
@@ -93,7 +93,7 @@ public function getType();
    * Returns the MIME type of the image file.
    *
    * @return string
-   *   The MIME type of the file, or an empty string if the file is invalid.
+   *   The MIME type of the image file.
    */
   public function getMimeType();
 
diff --git a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php
index 61c6ece..dfa8b90 100644
--- a/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php
+++ b/core/lib/Drupal/Core/ImageToolkit/ImageToolkitInterface.php
@@ -199,7 +199,6 @@ public function scaleAndCrop(ImageInterface $image, $width, $height);
    *   - "width": Width, in pixels.
    *   - "height": Height, in pixels.
    *   - "type": Image type represented as an IMAGETYPE_* constant.
-   *   - "mime_type": MIME type (e.g. 'image/jpeg', 'image/gif', 'image/png').
    *
    * @see \Drupal\Core\Image\ImageInterface::processInfo()
    */
diff --git a/core/modules/image/lib/Drupal/image/Plugin/Field/FieldWidget/ImageWidget.php b/core/modules/image/lib/Drupal/image/Plugin/Field/FieldWidget/ImageWidget.php
index 94528ae..cbb5c54 100644
--- a/core/modules/image/lib/Drupal/image/Plugin/Field/FieldWidget/ImageWidget.php
+++ b/core/modules/image/lib/Drupal/image/Plugin/Field/FieldWidget/ImageWidget.php
@@ -160,7 +160,7 @@ public static function process($element, &$form_state, $form) {
       }
       else {
         $image = \Drupal::service('image.factory')->get($file->getFileUri());
-        if ($image->getExtension()) {
+        if ($image->isExisting()) {
           $variables['width'] = $image->getWidth();
           $variables['height'] = $image->getHeight();
         }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/ImageToolkit/GDToolkit.php b/core/modules/system/lib/Drupal/system/Plugin/ImageToolkit/GDToolkit.php
index 1bd1d36..98e5572 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/ImageToolkit/GDToolkit.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/ImageToolkit/GDToolkit.php
@@ -309,7 +309,6 @@ public function getInfo(ImageInterface $image) {
         'width'     => $data[0],
         'height'    => $data[1],
         'type'      => $data[2],
-        'mime_type' => $data['mime'],
       );
     }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Image/ToolkitGdTest.php b/core/modules/system/lib/Drupal/system/Tests/Image/ToolkitGdTest.php
index d683b70..72ea5ad 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Image/ToolkitGdTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Image/ToolkitGdTest.php
@@ -253,7 +253,7 @@ function testManipulations() {
 
         $directory = $this->public_files_directory .'/imagetest';
         file_prepare_directory($directory, FILE_CREATE_DIRECTORY);
-        $image->save($directory . '/' . $op . '.' . $image->getExtension());
+        $image->save($directory . '/' . $op . '.' . $image->getDefaultExtension());
 
         $this->assertTrue($correct_dimensions_real, String::format('Image %file after %action action has proper dimensions.', array('%file' => $file, '%action' => $op)));
         $this->assertTrue($correct_dimensions_object, String::format('Image %file object after %action action is reporting the proper height and width values.', array('%file' => $file, '%action' => $op)));
diff --git a/core/modules/system/tests/modules/image_test/lib/Drupal/image_test/Plugin/ImageToolkit/TestToolkit.php b/core/modules/system/tests/modules/image_test/lib/Drupal/image_test/Plugin/ImageToolkit/TestToolkit.php
index d85d813..862129d 100644
--- a/core/modules/system/tests/modules/image_test/lib/Drupal/image_test/Plugin/ImageToolkit/TestToolkit.php
+++ b/core/modules/system/tests/modules/image_test/lib/Drupal/image_test/Plugin/ImageToolkit/TestToolkit.php
@@ -59,7 +59,6 @@ public function getInfo(ImageInterface $image) {
         'width'     => $data[0],
         'height'    => $data[1],
         'type'      => $data[2],
-        'mime_type' => $data['mime'],
       );
     }
 
diff --git a/core/tests/Drupal/Tests/Core/Image/ImageTest.php b/core/tests/Drupal/Tests/Core/Image/ImageTest.php
index d2c5fd7..ca1576a 100644
--- a/core/tests/Drupal/Tests/Core/Image/ImageTest.php
+++ b/core/tests/Drupal/Tests/Core/Image/ImageTest.php
@@ -78,10 +78,10 @@ protected function getToolkitMock(array $stubs = array()) {
   }
 
   /**
-   * Tests \Drupal\Core\Image\Image::getExtension().
+   * Tests \Drupal\Core\Image\Image::getDefaultExtension().
    */
   public function testGetExtension() {
-    $this->assertEquals($this->image->getExtension(), 'png');
+    $this->assertEquals($this->image->getDefaultExtension(), 'png');
   }
 
   /**