Fast techniques for searching images using the hausdorff distance

Abstract

Fast, low-overhead implementations of a powerful, reliable image matching engine based on the Hausdorff distance are disclosed. In one such implementation, a method is provided in which a processor receives two inputs. The first input is a pattern to be recognized in an image; the second, a digital image in which the pattern is to be recognized. The digital image is preprocessed with the processor using various morphological dilation operations so as to produce a set of preprocessed digital images. Thereafter, the processor performs a hierarchical search for the pattern in the digital image. The hierarchical search is performed over a search space, and includes a series of decisions, each decision indicating whether a portion of the search space can be eliminated from the search. Each decision is made by performing a plurality of comparisons between the pattern and the preprocessed digital images of the set and analyzing the results of these comparisons. Once the search is complete, the processor outputs a search outcome indicating, for example, whether (and where) the pattern has been found in the image. Any application domain wherein images are searched for instances of patterns can benefit from this invention. Document analysis applications provide one such domain.