Added pixel -> kvec function

src/fourier/details/euclidian_maps.hpp

@@ -131,6 +131,20 @@ namespace CosmoTool
         }
     }
 
+    template<typename Array2>
+    void get_Kvec(long p, Array2& kvec)
+    {
+      const DimArray& dims = this->getDims();
+      DimArray d(delta_k.size());
+      for (int q = 0; q < d.size(); q++)
+       {
+         d[q] = p%dims[q];
+         p = (p-d[q])/dims[q];
+       }
+      return get_Kvec(d, kvec);
+    }
+
+
     template<typename Array>
     double get_K(const Array& ik)
     {