def drift_vector_from_drift_matrix(drift_matrix):
''' Returns a list of tuples that represents the optimized drift vector.
:param drift_matrix: A NxN matrix that contains the measured drift between N images.
'''
barycenters = [tools.mean_of_list_of_tuples(row) for row in drift_matrix]
# print 'List of centers: ', centers
mod_matrix = [[tuple(map(operator.sub, cell, barycenters[i]))
for cell in row]
for i, row in enumerate(drift_matrix)]
# print 'Modified drift matrix:'
# pprint.pprint(mod_matrix)
rot_matrix = [list(x) for x in zip(*mod_matrix)]
# print 'Rotated matrix:'
# pprint.pprint(rot_matrix)
drift_vector = [tup
for tup in [tools.mean_of_list_of_tuples(row)
for row in rot_matrix
]
]
return drift_vector
