Estimation of recursive order number of a photocopied document through entropy from gray level co-occurrence matrix

摘要

Photocopy documents are very common in our normal life. In country like India, people are permitted to carry and present photocopied documents to avoid damages to the original documents. But this provision is misused for temporary benefits by fabricating fake photocopied documents. Fabrication of fake photocopied document is possible only in 2^nd and higher recursive order of photocopies. Whenever a photocopied document is submitted in place of original document, it may be required to check its originality. When the document is 1^st order photocopy, chances of fabrication can be ignored. On the other hand when the photocopy recursive order is 2 or above, probability of fabrication may be suspected. Hence when a photocopied document is presented instead of original document, the recursive order number of photocopy is to be estimated to ascertain the originality. This requirement demands to investigate a method to estimate order number of photocopy. It is noticed that the degradation in photocopy obtained increases as the recursive order of photocopy increases. Considering the degradation as a feature in this work, a method based on entropy from gray level co-occurrence matrix is proposed to estimate the recursive order number of the photocopied document through computing degradation rate. A detailed experimentation is performed on a generated data set and the method exhibits efficiency close to 95%.