info:eu-repo/semantics/doctoralThesis
An object description and categorization method based on shape and appearance features
Autor
LEONARDO CHANG FERNANDEZ
Resumen
Object recognition in images is one of the oldest problems in Computer Vision. In
this thesis, we focus on the problem of category-level object recognition, based on the
use of shape features as a more generic representation of object classes than appearance
features, while the latest are used as second-level features.
In this research work we propose an invariant shape feature extraction, description and
matching method for binary images, named LISF. The proposed method extracts local
features from the contour to describe shape and these features are later matched globally.
Combining local features with global matching allows us to obtain a trade-off between
discriminative power and robustness to noise and occlusion in the contour. The proposed
extraction, description and matching methods are invariant to rotation, translation and
scale, and present certain robustness to partial occlusion. The conducted experiments
showed that, for larger occlusion levels, the better was the performance of LISF with
respect to other popular shape description methods, with about 20% higher bull's eye
score and 25% higher accuracy in classification in images with a 60% occlusion. Also, we
present a massively parallel implementation in GPU of LISF, which achieves a speed-up
of up to 34x.
In order to deal with the intrinsic problems derived from using edges extracted from
real images, in this thesis we propose a shape descriptor, named OCTAR, that is particularly
suitable for partial shape matching of open/closed contours extracted from edgemap
images. Based on this descriptor, we also propose a partial shape matching method robust
to partial occlusion, noise, rotation and translation. Our approach allows to combine
shape and appearance through the evaluation of object detection hypothesis based on its
appearance, providing more distinctiveness. The conducted experiments showed competitive
results compared to the state of the art, in both binary and gray scale images.
Materias
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