access icon free Revealing the traces of histogram equalisation in digital images

The popular histogram equalisation (HE) technique, which was developed to improve the image contrast, sometimes may also be misused to hide intensity variations in tampered images with ill intention. The authors investigate how existing image forensic techniques may fail to detect HE operation in highly compressed and low-resolution images. They then propose an algorithm to detect whether a given image (either uncompressed or JPEG compressed) has undergone the HE process or not. It is based on the frequency domain analysis of image histogram and exploits the difference in DC and AC coefficients in histogram's discrete Fourier transform. It can detect HE operation even if the image is saved in JPEG format after the equalisation, where most the existing algorithms fail. The extensive computer simulations over large dataset show the effectiveness of the proposed algorithm.

Inspec keywords: discrete Fourier transforms; image coding; data compression; equalisers; image resolution; image forensics; frequency-domain analysis

Other keywords: AC coefficient; image resolution; JPEG format; compressed imaging; frequency domain analysis; image forensic technique; image contrast improvement; DC coefficient; HE technique; histogram equalisation technique; digital imaging; discrete Fourier transform

Subjects: Computer vision and image processing techniques; Integral transforms; Integral transforms; Image and video coding

http://iet.metastore.ingenta.com/content/journals/10.1049/iet-ipr.2017.0992
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