Robust Color Image Hashing with NMF and Saliency Map for Copy Detection

Image hashing is an effective technique for copy detection. This paper proposes a robust color image hashing scheme with Nonnegative Matrix Factorization (NMF) and saliency map. The proposed hashing scheme constructs a weighted feature map via the saliency map and the matrix of color vector angles. It extracts hash from the weighted feature map by using 2D Discrete Wavelet Transform (DWT), NMF, and ordinal measures. The use of 2D DWT achieves initial data reduction, the NMF provides a parts-based representation, and the ordinal measures can make a short and robust sequence. These techniques jointly contribute to a robust, short, and discriminative hash. Experiments of classification and copy detection are both done. Comparative results indicate that the proposed hashing scheme outperforms the compared hashing schemes.