Affine-invariant region detection is the basic technique for visual matching and has been widely applied in many areas. In this paper, we propose a simple yet effective method to detect the affine-invariant regions from gray image, which is called enclosed region. The enclosed region is detected based on the observation that one physical object is enclosed by the same region before and after affine transformation. The proposed method is a three-step method. Firstly, we segment the initial regions by using thresholds on the image. Secondly, external enclosing region (EER) and internal enclosed region (IER) are defined for each initial region, and we select the enclosed regions from the initial regions through applying histogram constraints on EER and IER. Thirdly, the largely overlapping regions are removed. Experiments on typical images exhibit the robustness of the proposed enclosed region detector. Extensively quantitative evaluation and comparison demonstrate that the proposed method outperforms state-of-the-art methods. © 2009 Elsevier Inc. All rights reserved.
Zhang, W., Wu, Q. M. J., Wang, G., You, X., & Wang, Y. (2010). Image matching using enclosed region detector. Journal of Visual Communication and Image Representation, 21(4), 271–282. https://doi.org/10.1016/j.jvcir.2009.11.001