Add support to extend for extendWith, allows copy/mirror/repeat (#3556)

lib/resize.js

@@ -36,6 +36,18 @@ const position = {
   'left top': 8
 };
 
+/**
+ * How to extend the image.
+ * @member
+ * @private
+ */
+const extendWith = {
+  background: 'background',
+  copy: 'copy',
+  repeat: 'repeat',
+  mirror: 'mirror'
+};
+
 /**
  * Strategies for automagic cover behaviour.
  * @member
@@ -393,6 +405,13 @@ function extend (extend) {
       }
     }
     this._setBackgroundColourOption('extendBackground', extend.background);
+    if (is.defined(extend.extendWith)) {
+      if (is.string(extendWith[extend.extendWith])) {
+        this.options.extendWith = extendWith[extend.extendWith];
+      } else {
+        throw is.invalidParameterError('extendWith', 'valid value', extend.extendWith);
+      }
+    }
   } else {
     throw is.invalidParameterError('extend', 'integer or object', extend);
   }