Lesson plan
Complex wavelet transform
The complex wavelet transform (CWT) is a complex-valued extension to the standard discrete wavelet transform (DWT). It is a two-dimensional wavelet transform which provides multiresolution, sparse representation, and useful characterization of the structure of an image. Further, it purveys a high degree of shift-invariance in its magnitude, which was investigated in. However, a drawback to this transform is that it exhibits 2^{d} (where d is the dimension of the signal being transformed) redundancy compared to a separable (DWT). The use of complex wavelets in image processing was originally set up in 1995 by J.M. Lina and L. Gagnon in the framework of the Daubechies orthogonal filters banks. It was then generalized in 1997 by Nick Kingsbury of Cambridge University. In the area of computer vision, by exploiting the concept of visual contexts, one can quickly focus on candidate regions, where objects of interest may be found, and then compute additional features through the CWT for those regions only. These additional features, while not necessary for global regions, are useful in accurate detection and recognition of smaller objects.…
Article summary
The complex wavelet transform (CWT) is a complex-valued extension to the standard discrete wavelet transform (DWT). It is a two-dimensional wavelet transform which provides multiresolution, sparse representation, and useful characterization of the structure of an image. Further, it purveys a high degree of shift-invariance in its magnitude, which was investigated in. However, a drawback to this transform is that it exhibits 2^{d} (where d is the dimension of the signal being transformed) redundancy compared to a separable (DWT). The use of complex wavelets in image processing was originally set up in 1995 by J.M. Lina and L. Gagnon in the framework of the Daubechies orthogonal filters banks. It was then generalized in 1997 by Nick Kingsbury of Cambridge University. In the area of computer vision, by exploiting the concept of visual contexts, one can quickly focus on candidate regions, where objects of interest may be found, and then compute additional features through the CWT for those regions only. These additional features, while not necessary for global regions, are useful in accurate detection and recognition of smaller objects.…
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
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