Abstract
Image rotation is a common auxiliary method of image tampering, which can make the forged image more realistic from the geometric perspective. Most algorithms of image rotation angle estimation employ the peak value on the Fourier spectrum; however, JPEG post-processing brings additional peak interferences to the spectrum, which has a great impact on algorithm performance. In this paper, angle estimation is carried out for images compressed by JPEG. Firstly, the Fourier cyclic spectrum of image covariance is calculated, followed by semi-soft threshold wavelet transform to eliminate the block artefacts brought by JPEG compression. According to the shortest distance principle in the range of the limited amplitude, the processed cyclic spectral data are sorted to select the peak points. Finally, according to the selected peak point, the corresponding position coordinates of the theoretical peak point are found, and the rotation angle of the image is estimated by the theoretical peak point. Experimental results demonstrate that the average absolute error of the proposed algorithm is significantly lower than that of the state-of-the-art methods investigated, which highlights the promising potential of the proposed method as an image resampling detector in practical forensics applications.
Highlights
Images are one of the important ways for people to obtain information
(2) When quality factors (QFs) = 95, true positive rate (TP) for the proposed algorithm was 83.55%, while it was 76.57% for Chen et al and 76.57% for Vazquez-Padin et al The results show that the semi-soft threshold wavelet transform could effectively improve the detection performance of the algorithm for JPEG
JPEG compression often brings additional peak interference to the cyclic spectrum, and destroys the resampling trace caused by the rotation angle, causing some interference with the selection of calculation points
Summary
Images are one of the important ways for people to obtain information. every coin has two sides; with the popularization of various image editing tools, people can recreate images in their own way, but the authenticity of the image cannot be guaranteed, and fake images affect people’s life in different aspects. The defect of this algorithm lies in the inaccurate estimation of the image scaling factor and the inability to detect down-sampling operations To avoid this problem, Wei et al [8] improved Gallagher’s algorithm, derived a detection formula for image down-sampling, and proposed a method to estimate rotation angle. Based on the existing algorithms, this paper further studies image rotation angle estimation with JPEG compression. In order to reduce the peak interference caused by JPEG compression, the amplitude data around the theoretical trajectory in the cyclic spectrum are processed by wavelet transform with a semi-soft threshold. In terms of the selection method, unlike the algorithms which select the maximum amplitude, this paper considers the amplitude and distance conditions comprehensively, selects the appropriate peak point, and calculates the corresponding theoretical point to estimate the rotation angle of an image.
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