pywt.swt2 un able to compute more than 1 level

[Xareni Galindo]

Hello all! 

Am trying to apply an swt2 wavelet function to an organoid tiff image (2d) but every time I set the level to anything bigger than one I get the same error, ValueError: start_level must be less than 1. I have been trying to find the solution on the web but I did not read any similar problem on this mailing list or any website. Can someone explain to me what is happening? I am maybe not applying the correct wavelet? or something that maybe I am not understanding on the documentation? So far, I have tried different wavelets and different level combinations and I have the same problem every time the level is not equal to 1.

My code is : 

path = 'C:/Users/Xareni Galindo/Pictures/'

filename = '60xclose-3_w3soSPIM-561_s5-1to85-1.tif'

# Load image

original = Image.open(path + filename)

coeffs= pywt.swt2(original, 'sym9', 2, start_level=0) # applying the wavelet to the image

output message

ValueError: start_level must be less than 1.

Thank you in advance

Xareni Galindo

[Kraig Fernandes]

Hey! I am facing the same issue when trying to use swt2 on my eeg signal, I can't seem to find a solution online. Were you able to rectify this error?

Regards, 

Kraig Fernandes

[Gregory Lee]

Hi Kraig,

My first guess would be that your signal has an odd length so that you need to pad (or truncate) it to a multiple of 2**n in order to be able to do a transform with n levels. See the Notes section of the swt2 docs.

https://pywavelets.readthedocs.io/en/latest/ref/swt-stationary-wavelet-transform.html#multilevel-2d-swt2

If that doesn't help, please post the signal size and exactly how you are calling the function.

Cheers,

Greg

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