Hierarchical Image Representation Using Deep Network

Abstract

In this paper, we propose a new method for features learning from unlabeled data. Basically, we simulate k-means algorithm in deep network architecture to achieve hierarchical Bag-of-Words (BoW) representations. We first learn visual words in each layer which are used to produce BoW feature vectors in the current input space. We transform the raw input data into new feature spaces in a convolutional manner such that more abstract visual words are extracted at each layer by implementing Expectation-Maximization (EM) algorithm. The network parameters are optimized as we keep the visual words fixed in the Expectation step while the visual words are updated with the current parameters of the network in the Maximization step. Besides, we embed spatial information into BoW representation by learning different networks and visual words for each quadrant regions. We compare the proposed algorithm with the similar approaches in the literature using a challenging 10-class-dataset, CIFAR-10.