Forensic Medicine Division, National Forensic Services, Seoul, South Korea.
Forensic Sci Int. 2012 Jan 10;214(1-3):200-6. doi: 10.1016/j.forsciint.2011.08.009. Epub 2011 Sep 3.
This paper describes a method for verifying the authenticity of a seal impression imprinted on a document based on the seal overlay metric, which refers to the ratio of an effective seal impression pattern and the noise in the neighborhood of the reference impression region. A reference seal pattern is obtained by taking the average of a number of high-quality impressions of a genuine seal. A target seal impression to be examined, often on paper with some background texts and lines, is segmented out from the background by an adaptive threshold applied to the histogram of color components. The segmented target seal impression is then spatially aligned with the reference by maximizing the count of matching pixels. Then the seal overlay metric is computed for the reference and the target. If the overlay metric of a target seal is below a predetermined limit for the similarity to the genuine, then the target is classified as a forged seal. To further reduce the misclassification rate, the seal overlay metric is adjusted by the filling rate, which reflects the quality of inked pattern of the target seal. Experiment results demonstrate that the proposed method can detect elaborate seal impressions created by advanced forgery techniques such as lithography and computer-aided manufacturing.
本文提出了一种基于印章叠印度量的方法来验证文件上的印章印记的真实性，该度量是指有效印章印记图案与参考印记区域附近噪声的比值。参考印章图案是通过对大量高质量真实印章的印记取平均值得到的。目标印章印记通常是在带有一些背景文本和线条的纸张上，通过对颜色分量的直方图应用自适应阈值将其从背景中分割出来。然后，通过最大化匹配像素的数量将分割后的目标印章印记与参考印章进行空间对齐。然后计算参考印章和目标印章的印章叠印度量。如果目标印章的叠印度量低于与真实印章相似度的预定限值，则将目标分类为伪造印章。为了进一步降低误分类率，通过填充率调整印章叠印度量，填充率反映了目标印章的油墨图案质量。实验结果表明，该方法可以检测到经过先进伪造技术（如光刻和计算机辅助制造）精心制作的印章印记。
