Rotation and scale invariant wavelet feature for content-based texture image retrieval
Journal of the American Society for Information Science and Technology
A wavelet based multiresolution algorithm for rotation invariant feature extraction
Pattern Recognition Letters
Explicit invariance of Cartesian Zernike moments
Pattern Recognition Letters
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We propose a general framework for extracting rotation invariant features from images for the tasks of image analysis and classification. Our framework is inspired in the form of the Zernike set of orthogonal functions. It provides a way to use a set of one-dimensional functions to form an orthogonal set over the unit disk by non-linearly scaling its domain, and then associating it an exponential term. When the images are projected into the subspace created with the proposed framework, the rotations in the image affect only the exponential term while the value of the orthogonal functions serve as rotation invariant features. We exemplify our framework using the Haar wavelet functions to extract features from several thousand images of symbols. We then use the features in an OCR experiment to demonstrate the robustness of the method.