Multiscale Corner Detection in Planar Shapes
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This paper presents a multiscale corner detection method in planar shapes, which applies an undecimated Mexican hat wavelet decomposition of the angulation signal to identify significant points on a shape contour. The advantage of using this wavelet is that it is well suited for detecting singularities as corners and contours due to its excellent selectivity in position. Thus, this wavelet plays an important role in our approach because it identifies changes in non-stationary angulation signals, and it can be extended to multidimensional approaches in an efficient way when approximating this wavelet by difference of Gaussians. The proposed algorithm detects peaks on a correlation signal which is generated from different wavelet scales and retains relevant points on the decomposed angulation signal while discards poor information. Our approach assumes that only peaks which persist through several scales correspond to corners. Furthermore, we introduce a novel procedure to tune parameters for the corner detection algorithms that corresponds to the best relation between Precision and Recall measures. This technique guides the parameter adjustment of the algorithms according to the image database and it improves their performance with regard to true corner detection. Concerning the performance assessment of the algorithms, we compare the proposed one to other corner detectors by using Precision and Recall measures which are based on ground-truth information. Tests were carried out using more than a hundred images from a non-homogenous database that contains noisy and non-noisy binary shapes.
KeywordsCorner detection High curvature points (HCP) Mexican hat wavelet Curvature space-scale
The authors are grateful to CNPq and FUNCAP for the support and financial help. Also, it was partially supported by the Office of Energy Research, U.S. Department of Energy, under Contract Number DE-AC02-05CH11231. We thank Prof. Barcellos for the helpful discussions and her student Glauco Pedrosa for providing and explaining his source code. And we are also thankful to Carlos W.D. de Almeida for the available CSS source code.
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