diff --git a/focal_point.effects.inc b/focal_point.effects.inc
index c6b9a17..f6d2826 100644
--- a/focal_point.effects.inc
+++ b/focal_point.effects.inc
@@ -37,14 +37,26 @@ function focal_point_image_effect_info() {
  * @return array
  *   Image effects keyed by effect machine name, containing an array of:
  *   - optionally: 'focal_point_disabled_by_default' = TRUE
- *   - any other key => value pairs are info which should be overwritten in
- *     hook_image_effect_info_alter().
+ *   - 'altered_info':  an array of properties which should be overwritten
+ *                      in hook_image_effect_info_alter().
+ *   - 'original_info': the original property values. (This is used to
+ *                      determine if another module already altered them.
+ *                      All callbacks which are altered must be defined here.
+ *
+ * @see focal_point_image_effect_info_alter()
+ * @see _focal_point_original_effect_callback()
  */
 function focal_point_image_effect_alter_info() {
   $alter_info = array(
     'image_scale_and_crop' => array(
-      'effect callback' => 'focal_point_image_scale_and_crop_effect',
-      'form callback' => 'focal_point_image_scale_and_crop_form',
+      'original_info' => array(
+        'effect callback' => 'image_scale_and_crop_effect',
+        'form callback' => 'image_resize_form',
+      ),
+      'altered_info' => array(
+        'effect callback' => 'focal_point_image_scale_and_crop_effect',
+        'form callback' => 'focal_point_image_scale_and_crop_form',
+      ),
     ),
     'image_crop' => array(
       /* This is disabled by default: enabling it would mean existing Crop
@@ -66,8 +78,14 @@ function focal_point_image_effect_alter_info() {
        * 'no setting' and 'saved setting of 50,50'.
        */
       'focal_point_disabled_by_default' => TRUE,
-      'effect callback' => 'focal_point_image_crop_effect',
-      'form callback' => 'focal_point_image_crop_form',
+      'original_info' => array(
+        'effect callback' => 'image_crop_effect',
+        'form callback' => 'image_crop_form',
+      ),
+      'altered_info' => array(
+        'effect callback' => 'focal_point_image_crop_effect',
+        'form callback' => 'focal_point_image_crop_form',
+      ),
     ),
   );
 
@@ -92,24 +110,53 @@ function focal_point_default_enabled_effects() {
 function focal_point_image_effect_info_alter(&$effects) {
   // Add focal_point capabilities to the standard effects. (This may deprecate
   // our own effects, eventually.)
-  foreach (focal_point_image_effect_alter_info() as $effect => $info) {
-    if (isset($effects[$effect])) {
+  $pre_altered_info = array();
+  foreach (focal_point_image_effect_alter_info() as $effect => $alter_info) {
+    if (isset($effects[$effect]) && isset($alter_info['altered_info'])) {
       // Alter values for this effect
-      foreach ($info as $key => $value) {
-        if ($key != 'off_by_default') {
-          $effects[$effect][$key] = $value;
+      foreach ($alter_info['altered_info'] as $key => $value) {
+        if (isset($alter_info['original_info'])
+            && $effects[$effect][$key] !== $alter_info['original_info']) {
+          // This value was already altered by something else; keep it.
+          $pre_altered_info[$effect][$key] = $effects[$effect][$key];
         }
+        $effects[$effect][$key] = $value;
       }
     }
   }
+
+  // Do we have any pre-altered values which are not equal to the original ones?
+  // Then keep them for later use.
+  if ($pre_altered_info) {
+    variable_set('focal_point_effect_pre_altered_info', $pre_altered_info);
+  }
+  elseif (variable_get('focal_point_effect_pre_altered_info')) {
+    variable_del('focal_point_effect_pre_altered_info');
+  }
+}
+
+/**
+ * Returns an 'original' (before we altered the info) callback for an effect.
+ */
+function _focal_point_original_effect_callback($callback_type, $effect_name) {
+  $pre_altered_info = variable_get('focal_point_effect_pre_altered_info', array());
+  if (isset($pre_altered_info[$effect_name]["$callback_type callback"])) {
+    // The callback was already altered before we altered it; return that.
+    return $pre_altered_info[$effect_name]["$callback_type callback"];
+  }
+
+  // Return the original function name.
+  $info = focal_point_image_effect_alter_info();
+  return $info[$effect_name]['original_info']["$callback_type callback"];
 }
 
 /**
  * Form builder for the 'image_scale_and_crop' form (overridden).
  */
 function focal_point_image_scale_and_crop_form($data = array()) {
-  // The original form callback:
-  $form = image_resize_form($data);
+
+  $function = _focal_point_original_effect_callback('form', 'image_scale_and_crop');
+  $form = $function($data);
 
   $form['focal_point_use'] = array(
     '#type' => 'select',
@@ -130,8 +177,9 @@ function focal_point_image_scale_and_crop_form($data = array()) {
  * Form builder for the 'image_crop' form (overridden).
  */
 function focal_point_image_crop_form($data = array()) {
-  // The original form callback:
-  $form = image_crop_form($data);
+
+  $function = _focal_point_original_effect_callback('form', 'image_crop');
+  $form = $function($data);
 
   $form['focal_point_use'] = array(
     '#type' => 'select',
@@ -155,11 +203,12 @@ function focal_point_image_crop_form($data = array()) {
  * Image effect callback for the 'image_scale_and_crop' form (overridden).
  */
 function focal_point_image_scale_and_crop_effect(&$image, $data) {
-  if (focal_point_effect_use_focal_point($data, 'image_scale_and_crop')) {
+  if (focal_point_effect_uses_focal_point($data, 'image_scale_and_crop')) {
     return focal_point_scale_and_crop_effect($image, $data);
   }
 
-  return image_scale_and_crop_effect($image, $data);
+  $function = _focal_point_original_effect_callback('effect', 'image_scale_and_crop');
+  return $function($image, $data);
 }
 
 /**
@@ -178,14 +227,16 @@ function focal_point_scale_and_crop_effect(&$image, $data) {
 
   // At worst use the default effect and let Drupal handle the errors that
   // likely exist at this point.
-  return image_scale_and_crop_effect($image, $data);
+  $function = _focal_point_original_effect_callback('effect', 'image_scale_and_crop');
+  return $function($image, $data);
 }
 
 /**
  * Form builder for the crop form.
  */
 function focal_point_crop_form($data = array()) {
-  $form = image_crop_form($data);
+  $function = _focal_point_original_effect_callback('form', 'image_crop');
+  $form = $function($data);
   unset($form['anchor']);
 
   return $form;
@@ -195,11 +246,12 @@ function focal_point_crop_form($data = array()) {
  * Image effect callback for the 'image_crop' form (overridden).
  */
 function focal_point_image_crop_effect(&$image, $data) {
-  if (focal_point_effect_use_focal_point($data, 'image_crop')) {
+  if (focal_point_effect_uses_focal_point($data, 'image_crop')) {
     return focal_point_crop_effect($image, $data);
   }
 
-  return image_crop_effect($image, $data);
+  $function = _focal_point_original_effect_callback('effect', 'image_crop');
+  return $function($image, $data);
 }
 
 /**
@@ -212,7 +264,8 @@ function focal_point_crop_effect(&$image, $data) {
 
   // At worst use the default effect and let Drupal handle the errors that
   // likely exist at this point.
-  return image_crop_effect($image, $data);
+  $function = _focal_point_original_effect_callback('effect', 'image_crop');
+  return $function($image, $data);
 }
 
 /**
@@ -309,7 +362,7 @@ function focal_point_effect_resize_data($image_width, $image_height, $crop_width
  *
  * @return bool
  */
-function focal_point_effect_use_focal_point($data, $effect) {
+function focal_point_effect_uses_focal_point($data, $effect) {
   if (!empty($data['focal_point_use'])) {
     // There is an attribute in this effect's config:
     // Value should be 'y' or 'n'. For unknown values, disable focal point.
diff --git a/focal_point.module b/focal_point.module
index 55036a9..c656c41 100644
--- a/focal_point.module
+++ b/focal_point.module
@@ -629,7 +629,7 @@ function _focal_point_get_image_styles($altered_only = FALSE) {
       $focal_point_style = in_array($effect['name'], $focal_point_effects, TRUE);
       if (!$focal_point_style) {
         // Is this effect configured to use focal point?
-        $focal_point_style = focal_point_effect_use_focal_point($effect['data'], $effect['name']);
+        $focal_point_style = focal_point_effect_uses_focal_point($effect['data'], $effect['name']);
       }
 
       if ($focal_point_style) {