Region based matching for print process identification

For quality inspection of security printing systems it is necessary to measure the displacement between printing processes. We present a new approach for region based matching of color images. Maximally stable extremal regions are extracted from image color channels and are the basis for matching. Binary template matching is performed between pairs of regions taken from the corresponding color channels of different images and a displacement vector is derived for each matching pair of regions. Clustering of measured displacements taken from sequences of sample images allows the estimation of the accuracy of printing processes and the alignment of printing processes. Results of an experimental application to banknote printing process inspection are given.