Removal of Color Scratches from Old Motion Picture Films Exploiting Human Perception
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Research Article Removal of Color Scratches from Old Motion Picture Films Exploiting Human Perception Vittoria Bruni, Paola Ferrara, and Domenico Vitulano Consiglio Nazionale delle Ricerche, Istituto per le Applicazioni del Calcolo “M. Picone”, Viale del Policlinico 137 00161 Roma, Italy Correspondence should be addressed to Vittoria Bruni, [email protected] Received 31 August 2007; Revised 8 April 2008; Accepted 15 July 2008 Recommended by Theodore Vlachos In this paper a unified model for both detection and restoration of line scratches on color movies is presented. It exploits a generalization of the light diffraction effect for modeling the shape of scratches, while perception laws are used for their automatic detection and removal. The detection algorithm has a high precision in terms of number of detected true scratches and reduced number of false alarms. The quality of the restored images is satisfying from a subjective (visual) point of view if compared with the state-of-the-art approaches. The use of very simple operations in both detection and restoration phases makes the implemented algorithms appealing for their low computing time. Copyright © 2008 Vittoria Bruni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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INTRODUCTION
The automatic detection and removal of degradation in film sequences is fundamental in the restoration process because of the huge number of the involved frames [1, 2]. To this aim, a really useful and effective restoration tool must involve oriented techniques that fully exploit the damage peculiarities. With regard to line scratches, different approaches have been proposed in the recent literature [1– 13]. Scratches appear as straight lines lying on much of the vertical extent of the frame. They can have different color while their width is in a limited range of pixels [1]. They are often caused by a mechanical stress during the projection of a movie so that they occupy the same or quite the same location in subsequent frames. That is why they cannot be classified as temporal impulsive defects. In [5, 6] a physical model for the observed scratches has been provided by proving that they are caused by light diffraction. In fact, a scratch is a thin slit on the film material that it is crossed by the light during the projection and/or the scanning process. Since a different amount of the original information is removed in the degradation process, according to the depth of the slit, the damaged area can be modeled as a partially missing data region. Moreover, simple rules of the Human Visual System [14] can guide both the detection and the
restoration processes. In particular, the scratch is detected as a visible object in the scene and it is removed by shrinking its contribution till it becomes negligible for the observer. Based on these assumptions, the method in [5, 6] for black and white (BW) movies presents t
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