Comparative study of image restoration techniques in forensic image processing

In this work we investigated the forensic applicability of some state-of-the-art image restoration techniques for digitized video-images and photographs: classical Wiener filtering, constrained Maximum Entropy, and some variants of constrained Minimum Total Variation. Basic concepts and experimental results are discussed. Because all methods appeared to produce different results, a discussion is given of which method is the most suitable, depending on the image objects that are questioned, prior knowledge and type of blur and noise. Constrained Minimum Total Variation methods produced the best results for test images with simulated noise and blur. In cases where images are the most substantial part of the evidence, constrained Maximum Entropy might be more suitable, because its theoretical basis predicts a restoration result that shows the most likely pixel values, given all the prior knowledge used during restoration.