Histogram-Based Perceptual Image Hashing in the DWT Domain

Media hashing is a compact representation of media content, one potential application of which is for content-based information retrieval. In the earlier work [13], the invariance of the spatial-domain histogram in shape to geometric deformations has been successfully exploited for image hashing. In this work, we extend the invariance into the discrete wavelet transform (DWT) domain to make this hashing scheme more flexible. As two important aspects, robustness and uniqueness of the proposed DWT hashing function are investigated in detail by representing the histogram shape as the relative relations in the number of the low-frequency coefficients among groups of two different histogram bins. Extensive tests show that the hashing scheme has a satisfactory performance to various geometric deformations and most common signal processing operations due to the use of the DWT-domain histogram and Gaussian kernel filter.