Fix that corrects the OpenCV's random access iterator distance: d(x,y) = -d(y,x)

modules/core/include/opencv2/core/mat.inl.hpp

@@ -2474,7 +2474,7 @@ ptrdiff_t operator - (const MatConstIterator& b, const MatConstIterator& a)
     if( a.m != b.m )
         return ((size_t)(-1) >> 1);
     if( a.sliceEnd == b.sliceEnd )
-        return (b.ptr - a.ptr)/b.elemSize;
+        return (b.ptr - a.ptr)/static_cast<ptrdiff_t>(b.elemSize);
 
     return b.lpos() - a.lpos();
 }