System for Screening Objectionable Images

James Ze Wang, Jia Li, Gio Wiederhold, Oscar Firschein
Stanford University, Stanford, CA 94305

As computers and Internet become more and more available to families, access of objectionable graphics by children is increasingly a problem that many parents are concerned about. This paper describes WIPE(TM) (Wavelet Image Pornography Elimination), a system capable of classifying an image as objectionable or benign. The algorithm uses a combination of an icon filter, a graph-photo detector, a color histogram filter, a texture filter, and a wavelet-based shape matching algorithm to provide robust screening of on-line objectionable images. Semantically-meaningful feature vector matching is carried out so that comparisons between a given on-line image and images in a pre-marked training data set can be performed efficiently and effectively. The system is practical for real-world applications, processing queries at the speed of less than 2 seconds each, including the time to compute the feature vector for the query, on a Pentium Pro PC. Besides its exceptional speed, it has demonstrated 96% sensitivity over a test set of 1,076 digital photographs found on objectionable news groups. It wrongly classified 9% of a set of 10,809 benign photographs obtained from various sources. The specificity in real-world applications is expected to be much higher because benign on-line graphs can be filtered out with our graph-photo detector with 100% sensitivity and nearly 100% specificity, and surrounding text can be used to assist the classification process.

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Citation: James Z. Wang, Jia Li, Gio Wiederhold and Oscar Firschein, ``System for Screening Objectionable Images,'' Computer Communications, vol. 21, no. 15, pp. 1355-1360, Elsevier, 1998.

Copyright 1998 Journal Computer Communications, Elsevier, Amsterdam, 1998. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the publisher.

Last Modified: 28-Jan-98 23:20:32 PST
1998, James Z. Wang