Criterial image preparation for a search method for digital watermarking image using correlation coefficient between pixel value histograms

An efficient two-stage image search method for the extraction of illegal copies on the Internet has been proposed in our previous paper. In the present paper, we propose a criterial image preparation method for more efficient searching in the pre-search stage. It is possible to accelerate searching without omission because the criterial image preparation method provides a criterial image set for the various attacks involving changes to known pixel values. In addition, we propose an improved pre-search algorithm that includes the extraction of a GIF-compression-attacked image involving color number transformation. The performance of the improved pre-search method is evaluated through computer simulation.