LatticeSearch: Return reindex matrix

image_analysis/lattice_search/LatticeSearch.cpp

@@ -339,6 +339,7 @@ LatticeSearchResult LatticeSearch(const CrystalLattice &L, double dist_tolerance
                 .conventional = L_niggli.Multiply(c.reindex),
                 .system = c.system,
                 .centering = c.centering,
+                    .reindex = c.reindex,
             };
         }
     }
@@ -349,5 +350,6 @@ LatticeSearchResult LatticeSearch(const CrystalLattice &L, double dist_tolerance
         .conventional = L_niggli,
         .system = gemmi::CrystalSystem::Triclinic,
         .centering = 'P',
+        .reindex = gemmi::Mat33(1, 0, 0, 0, 1, 0, 0, 0, 1),
     };
 }

image_analysis/lattice_search/LatticeSearch.h

@@ -16,6 +16,10 @@ struct LatticeSearchResult {
     CrystalLattice conventional;
     gemmi::CrystalSystem system = gemmi::CrystalSystem::Triclinic;
     char centering = 'P'; // 'P','A','B','C','I','F','R'
+
+    // Change-of-basis from primitive_reduced to conventional:
+    // conventional = primitive_reduced.Multiply(reindex)
+    gemmi::Mat33 reindex = gemmi::Mat33(1, 0, 0, 0, 1, 0, 0, 0, 1);
 };
 
 LatticeSearchResult LatticeSearch(const CrystalLattice& L, double dist_tolerance = 0.03, double angle_tolerance_deg = 3);