Learning Flexible Binary Code for Linear Projection Based Hashing with Random Forest

Existing linear projection based hashing methods have witnessed many progresses in finding the approximate nearest neighbor(s) of a given query. They perform well when using a short code. But their code length depends on the original data dimension, thus their performance can not be further improved with higher number of bits for low dimensional data. In addition, in the case of high dimensional data, it is not a good choice to produce each bit by a sign function. In this paper, we propose a novel random forest based approach to cope with the above shortcomings. The bits are obtained by recording the paths when a point traversing each tree in the forest. Then we propose a new metric to calculate the similarity between any two codes. Experimental results on two large benchmark datasets show that our approach outperforms its counterparts and demonstrate its superiority over the existing state-of-the-art hashing methods for descriptor retrieval.