fixed compile error under win32

diff --git a/modules/features2d/include/opencv2/features2d/features2d.hpp b/modules/features2d/include/opencv2/features2d/features2d.hpp
index b7f551a..a291911 100644 (file)
--- a/modules/features2d/include/opencv2/features2d/features2d.hpp
+++ b/modules/features2d/include/opencv2/features2d/features2d.hpp
@@ -1804,7 +1804,7 @@ struct CV_EXPORTS L2
             ResultType diff = a[i] - b[i];
             result += diff*diff;
         }
-        return sqrt(result);
+        return (ResultType)sqrt((double)result);
     }
 };