fix pyvista surface mesh

src/gnomon_package_tissueimagemesh/algorithm/meshFromImage/surfaceMeshPyvista.py

@@ -81,7 +81,7 @@ class surfaceMeshPyvista(gnomonAbstractMeshFromImage):
             self._parameters['resampling_voxelsize'].setValue(4*np.mean(img.voxelsize))
 
     def run(self):
-        self.set_max_progress(4*len(self.img))
+        self.set_max_progress(5*len(self.img))
         self.topomesh = {}
 
         for time in self.img.keys():
@@ -152,7 +152,7 @@ class surfaceMeshPyvista(gnomonAbstractMeshFromImage):
             image_mesh = image_mesh.extract_points(
                 up_facing_points,
                 include_cells=True,
-            ).extract_surface()
+            ).extract_largest().extract_surface()
             self.increment_progress()
 
             self.set_progress_message(f"T {time} : Creating triangle mesh")