diff --git a/helper.js b/helper.js
index f36b4e5..dc3940b 100644
--- a/helper.js
+++ b/helper.js
@@ -107,6 +107,16 @@ async function unSelect() {
     return result
 }
 
+/**
+ * Convert 1d index to 2d array
+ * @param {number} index sequential index
+ * @param {number} width width of 2d array
+ * @returns {number[]} [x,y]
+ */
+function indexToXY(index, width) {
+    return [index % width, Math.floor(index / width)]
+}
+
 // async function layerToSelectionHelper () {
 //   // console.log("executeAsModal layer.translate")