code: def test_dense():
      f = np.arange(280 * 360).reshape((280, 360)) % 25
      d16 = surf.dense(f, 16)
      d16_s = surf.dense(f, 16, 3.0)
      d32 = surf.dense(f, 32)
  
      assert len(d16) > len(d32)
      assert d16.shape[1] == d32.shape[1]
      assert d16.shape[1] == d16_s.shape[1]
  
file_path: mahotas/mahotas/tests/test_surf.py
imports: import numpy
  import mahotas
  import mahotas.features.surf
  from mahotas.features import _surf
  from .utils import luispedro_jpg
  import pytest
label_desc: Use image node_id 13 for calling a global function with example usage: test_dense() without return types