Automatic seal image retrieval method by using shape features of Chinese characters

In many eastern countries, a large number of seal images need to be identified every day. The system compares an input seal image with its reference seal and validates the authenticity of it. However, the reference seal is usually found manually. As each reference seal has quite a long corresponding ID, inputting ID to get the needed seal one by one costs quite a lot of time and this manual stage has become the bottleneck of automatic seal identification. To make the seal verification system more automatic, a new retrieval method based on Chinese characters´ shape features will be introduced in this paper. Firstly, the main characters region is obtained by transforming the round seal image to a rectangle one and choosing the main part for each seal. Secondly, every single character is segmented using correlation method, and the number of characters in a seal can be got. Thirdly, four horizontal and four vertical features are extracted for each character in a seal and an eigenvector called position code is defined. Finally, the retrieval strategy is mainly based on transform from position code to a weight to decide which two seal images have the most similarity. Experiments on a database of 1000 testing seal images provide the retrieval ability for the proposed approach. The correct rate goes to 95.3%.