diff --git a/modules/simpletest/files/image-test-transparent-out-of-range.gif b/modules/simpletest/files/image-test-transparent-out-of-range.gif
new file mode 100644
index 00000000000..a54df7a93ce
Binary files /dev/null and b/modules/simpletest/files/image-test-transparent-out-of-range.gif differ
diff --git a/modules/simpletest/tests/image.test b/modules/simpletest/tests/image.test
index dc95a6e2fd7..849702216e9 100644
--- a/modules/simpletest/tests/image.test
+++ b/modules/simpletest/tests/image.test
@@ -261,6 +261,7 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
    */
   function testManipulations() {
     // If GD isn't available don't bother testing this.
+    module_load_include('inc', 'system', 'image.gd');
     if (!function_exists('image_gd_check_settings') || !image_gd_check_settings()) {
       $this->pass(t('Image manipulations for the GD toolkit were skipped because the GD toolkit is not available.'));
       return;
@@ -379,7 +380,7 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
             array_fill(0, 3, 76) + array(3 => 0),
             array_fill(0, 3, 149) + array(3 => 0),
             array_fill(0, 3, 29) + array(3 => 0),
-            array_fill(0, 3, 0) + array(3 => 127)
+            array_fill(0, 3, 225) + array(3 => 127)
           ),
         ),
       );
@@ -394,11 +395,14 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
           continue 2;
         }
 
-        // Transparent GIFs and the imagefilter function don't work together.
-        // There is a todo in image.gd.inc to correct this.
+        // All images should be converted to truecolor when loaded.
+        $image_truecolor = imageistruecolor($image->resource);
+        $this->assertTrue($image_truecolor, format_string('Image %file after load is a truecolor image.', array('%file' => $file)));
+
         if ($image->info['extension'] == 'gif') {
           if ($op == 'desaturate') {
-            $values['corners'][3] = $this->white;
+            // Transparent GIFs and the imagefilter function don't work together.
+            $values['corners'][3][3] = 0;
           }
         }
 
@@ -451,7 +455,8 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
 
         $directory = file_default_scheme() . '://imagetests';
         file_prepare_directory($directory, FILE_CREATE_DIRECTORY);
-        image_save($image, $directory . '/' . $op . '.' . $image->info['extension']);
+        $file_path = $directory . '/' . $op . '.' . $image->info['extension'];
+        image_save($image, $file_path);
 
         $this->assertTrue($correct_dimensions_real, format_string('Image %file after %action action has proper dimensions.', array('%file' => $file, '%action' => $op)));
         $this->assertTrue($correct_dimensions_object, format_string('Image %file object after %action action is reporting the proper height and width values.', array('%file' => $file, '%action' => $op)));
@@ -460,8 +465,37 @@ class ImageToolkitGdTestCase extends DrupalWebTestCase {
           $this->assertTrue($correct_colors, format_string('Image %file object after %action action has the correct color placement.', array('%file' => $file, '%action' => $op)));
         }
       }
-    }
 
+      // Check that saved image reloads without raising PHP errors.
+      $image_reloaded = image_load($file_path);
+    }
+  }
+
+  /**
+   * Tests loading an image whose transparent color index is out of range.
+   */
+  function testTransparentColorOutOfRange() {
+    // This image was generated by taking an initial image with a palette size
+    // of 6 colors, and setting the transparent color index to 6 (one higher
+    // than the largest allowed index), as follows:
+    // @code
+    // $image = imagecreatefromgif('modules/simpletest/files/image-test.gif');
+    // imagecolortransparent($image, 6);
+    // imagegif($image, 'modules/simpletest/files/image-test-transparent-out-of-range.gif');
+    // @endcode
+    // This allows us to test that an image with an out-of-range color index
+    // can be loaded correctly.
+    $file = 'image-test-transparent-out-of-range.gif';
+    $image = image_load(drupal_get_path('module', 'simpletest') . '/files/' . $file);
+
+    if (!$image) {
+      $this->fail(format_string('Could not load image %file.', array('%file' => $file)));
+    }
+    else {
+      // All images should be converted to truecolor when loaded.
+      $image_truecolor = imageistruecolor($image->resource);
+      $this->assertTrue($image_truecolor, format_string('Image %file after load is a truecolor image.', array('%file' => $file)));
+    }
   }
 }
 
diff --git a/modules/system/image.gd.inc b/modules/system/image.gd.inc
index d9035e4c683..913b0de5125 100644
--- a/modules/system/image.gd.inc
+++ b/modules/system/image.gd.inc
@@ -229,7 +229,24 @@ function image_gd_desaturate(stdClass $image) {
 function image_gd_load(stdClass $image) {
   $extension = str_replace('jpg', 'jpeg', $image->info['extension']);
   $function = 'imagecreatefrom' . $extension;
-  return (function_exists($function) && $image->resource = $function($image->source));
+  if (function_exists($function) && $image->resource = $function($image->source)) {
+    if (imageistruecolor($image->resource)) {
+      return TRUE;
+    }
+    else {
+      // Convert indexed images to truecolor, copying the image to a new
+      // truecolor resource, so that filters work correctly and don't result
+      // in unnecessary dither.
+      $resource = image_gd_create_tmp($image, $image->info['width'], $image->info['height']);
+      if ($resource) {
+        imagecopy($resource, $image->resource, 0, 0, 0, 0, imagesx($resource), imagesy($resource));
+        imagedestroy($image->resource);
+        $image->resource = $resource;
+      }
+    }
+    return (bool) $image->resource;
+  }
+  return FALSE;
 }
 
 /**
@@ -297,17 +314,31 @@ function image_gd_create_tmp(stdClass $image, $width, $height) {
   $res = imagecreatetruecolor($width, $height);
 
   if ($image->info['extension'] == 'gif') {
-    // Grab transparent color index from image resource.
+    // Find out if a transparent color is set, will return -1 if no
+    // transparent color has been defined in the image.
     $transparent = imagecolortransparent($image->resource);
 
     if ($transparent >= 0) {
-      // The original must have a transparent color, allocate to the new image.
-      $transparent_color = imagecolorsforindex($image->resource, $transparent);
-      $transparent = imagecolorallocate($res, $transparent_color['red'], $transparent_color['green'], $transparent_color['blue']);
+      // Find out the number of colors in the image palette. It will be 0 for
+      // truecolor images.
+      $palette_size = imagecolorstotal($image->resource);
+      if ($palette_size == 0 || $transparent < $palette_size) {
+        // Set the transparent color in the new resource, either if it is a
+        // truecolor image or if the transparent color is part of the palette.
+        // Since the index of the transparency color is a property of the
+        // image rather than of the palette, it is possible that an image
+        // could be created with this index set outside the palette size (see
+        // http://stackoverflow.com/a/3898007).
+        $transparent_color = imagecolorsforindex($image->resource, $transparent);
+        $transparent = imagecolorallocate($res, $transparent_color['red'], $transparent_color['green'], $transparent_color['blue']);
 
-      // Flood with our new transparent color.
-      imagefill($res, 0, 0, $transparent);
-      imagecolortransparent($res, $transparent);
+        // Flood with our new transparent color.
+        imagefill($res, 0, 0, $transparent);
+        imagecolortransparent($res, $transparent);
+      }
+      else {
+        imagefill($res, 0, 0, imagecolorallocate($res, 255, 255, 255));
+      }
     }
   }
   elseif ($image->info['extension'] == 'png') {