encoding.py 文件源码

def vlad(data, means, assignments, components, 
               normalize=['l2c']):
    """
    compute 'vector of locally aggregated descriptors'
    """
    def encode(k):
        uk_ = assignments[:,k].T.dot(data)        

        clustermass = assignments[:,k].sum()
        if clustermass > 0:
            uk_ -= clustermass * means[k]

        if 'l2c' in normalize:
            n = max(math.sqrt(np.sum(uk_ * uk_)), 1e-12)
            uk_ /= n

        return uk_

    uk = map(encode, range(components))

    uk = np.concatenate(uk, axis=0).reshape(1,-1)

    return uk