mexican hat wavelet transform on images using python

[Nachiket Patki]

Hello community,

I am working on a project where I have to use Mexican hat wavelet on images (python). When I tried using "pywt.wavedec2(imArray, 'mexh', level=level)" I am getting an error saying  " invalid wavelet name". 

I think its a continuous wavelet transform so my question is how to apply mexican hat on images? (means decomposing and reconstruction using cwt).

awaiting for reply

[Gregory Lee]

Hi Nachiket,

Unfortunately, only 1D transforms have been implemented for the continuous wavelet transform in PyWavelets. Unlike for the discrete wavelet transforms implemented in PyWavelets, the 2D CWT with the mexican hat is not a product of separable 1D transforms.  The 2D CWT could be implemented using 2D Fourier transforms to perform the non-separable filtering in the Fourier domain.  

I have never used it, but an example of this approach is available in an older branch of PyCWT:

https://github.com/duducosmos/kPyWavelet/blob/master/kPyWavelet/twod.py

- Greg

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[Nachiket Patki]

Thank you Greg for the wonderful reply. 

I will definitely go through this.

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