def test_prewitt_h_vertical():
 (i, j) = np.mgrid[(-5):6, (-5):6]
 image = (j >= 0).astype(float)
 result = filters.prewitt_h(image)
 assert_allclose(result, 0, atol=1e-10)

def test_prewitt_h_vertical ( ) : ( i , j ) = np . mgrid [ ( - 5 ) : 6 , ( - 5 ) : 6 ] image = ( j >= 0 ) . astype ( float ) result = filters . prewitt_h ( image ) assert_allclose ( result , 0 , atol = 1e-10 )
horizontal prewitt on a vertical edge should be zero .