Add null check in extractPaper

src/jscanify-node.js

@@ -141,6 +141,9 @@ class jscanify {
 
   /**
    * Extracts and undistorts the image detected within the frame.
+   * 
+   * Returns `null` if no paper is detected.
+   * 
    * @param {*} image image to process
    * @param {*} resultWidth desired result paper width
    * @param {*} resultHeight desired result paper height
@@ -151,6 +154,11 @@ class jscanify {
     const canvas = createCanvas();
     const img = cv.imread(image);
     const maxContour = this.findPaperContour(img);
+
+    if(maxContour == null){
+      return null;
+    }
+
     const {
       topLeftCorner,
       topRightCorner,

src/jscanify.js

@@ -132,7 +132,10 @@
 
     /**
      * Extracts and undistorts the image detected within the frame.
-     * @param {*} image image to process
+     * 
+     * Returns `null` if no paper is detected.
+     *  
+    * @param {*} image image to process
      * @param {*} resultWidth desired result paper width
      * @param {*} resultHeight desired result paper height
      * @param {*} cornerPoints optional custom corner points, in case automatic corner points are incorrect
@@ -140,11 +143,13 @@
      */
     extractPaper(image, resultWidth, resultHeight, cornerPoints) {
       const canvas = document.createElement("canvas");
-
       const img = cv.imread(image);
-
       const maxContour = this.findPaperContour(img);
 
+      if(maxContour == null){
+        return null;
+      }
+
       const {
         topLeftCorner,
         topRightCorner,