Use“ moms” replace "contourArea"

double area = moms.m00;
is same as
double area = contourArea(contours[contourIdx]);
Not to mention
"moms" already calculated here,"contourArea" should not apply

modules/features2d/src/blobdetector.cpp

@@ -257,7 +257,7 @@ void SimpleBlobDetectorImpl::findBlobs(InputArray _image, InputArray _binaryImag
         {
             std::vector < Point > hull;
             convexHull(contours[contourIdx], hull);
-            double area = contourArea(contours[contourIdx]);
+            double area = moms.m00;
             double hullArea = contourArea(hull);
             if (fabs(hullArea) < DBL_EPSILON)
                 continue;