diff --git a/alg/qrtool.cpp b/alg/qrtool.cpp
index 58c873c..3e51845 100644
--- a/alg/qrtool.cpp
+++ b/alg/qrtool.cpp
@@ -302,7 +302,7 @@ static void get_bin(Mat &orig, Mat &out)
     convertScaleAbs(gray, gray, 2);
     // bilateralFilter(gray, filtered, 9, 150, 150, BORDER_DEFAULT);
     medianBlur(gray, gray, 9);
-    threshold(gray, out, 128, 255, THRESH_BINARY);
+    adaptiveThreshold(gray, out, 255, ADAPTIVE_THRESH_GAUSSIAN_C, THRESH_BINARY, 11, 2);
 }
 
 static