- Patch #875326 by effulgentsia: add hook_image_effect_info_alter().

modules/image/image.api.php

@@ -29,6 +29,8 @@
  *     $form array providing a configuration form for this image effect.
  *   - "summary theme": (optional) The name of a theme function that will output
  *     a summary of this image effect's configuration.
+ *
+ * @see hook_image_effect_info_alter()
  */
 function hook_image_effect_info() {
   $effects = array();
@@ -44,6 +46,20 @@ function hook_image_effect_info() {
   return $effects;
 }
 
+/**
+ * Alter the information provided in hook_image_effect_info().
+ *
+ * @param $effects
+ *   The array of image effects, keyed on the machine-readable effect name.
+ *
+ * @see hook_image_effect_info()
+ */
+function hook_image_effect_info_alter(&$effects) {
+  // Override the Image module's crop effect with more options.
+  $effect['image_crop']['effect callback'] = 'mymodule_crop_effect';
+  $effect['image_crop']['form callback'] = 'mymodule_crop_form';
+}
+
 /**
  * Respond to image style updating.
  *

modules/image/image.module

@@ -912,6 +912,7 @@ function image_effect_definitions() {
         }
       }
       uasort($effects, '_image_effect_definitions_sort');
+      drupal_alter('image_effect_info', $effects);
       cache_set("image_effects:$langcode", $effects);
     }
   }