Semi-automatic wavelet soft-thresholding applied to digital image error level analysis
- Published
- Accepted
- Subject Areas
- Artificial Intelligence, Computer Vision, Data Mining and Machine Learning, Graphics
- Keywords
- wavelet, thresholding, error level analysis, image forensics, forgery detection
- Copyright
- © 2016 Jeronymo
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2016. Semi-automatic wavelet soft-thresholding applied to digital image error level analysis. PeerJ Preprints 4:e2619v1 https://doi.org/10.7287/peerj.preprints.2619v1
Abstract
In this paper a method for detection of image forgery in lossy compressed digital images known as error level analysis (ELA) is presented and it's noisy components are filtered with automatic wavelet soft-thresholding. With ELA, a lossy compressed image is recompressed at a known error rate and the absolute differences between these images, known as error levels, are computed. This method might be weakened if the image noise generated by the compression scheme is too intense, creating the necessity of noise filtering. Wavelet thresholding is a proven denoising technique which is capable of removing an image's noise avoiding altering other components, like high frequencies regions, by thresholding the wavelet transform coefficients, thus not causing blurring. Despite its effectiveness, the choice of the threshold is a known issue. However there are some approaches to select it automatically. In this paper, a lowpass filter is implemented through wavelet thresholding, attenuating error level noises. An efficient method to automatically determine the threshold level is used, showing good results in threshold selection for the presented problem. Standard test images have been doctored to simulate image tampering, error levels for these images are computed and wavelet thresholding is performed to attenuate noise. Results are presented, confirming the method's efficiency at noise filtering while preserving necessary error levels.
Author Comment
This is a submission to PeerJ Computer Science for review.