nabu.reconstruction.filtering module

class nabu.reconstruction.filtering.SinoFilter(sino_shape, filter_name=None, padding_mode='zeros', extra_options=None)

Bases: object

available_filters = ['ramlak', 'shepp-logan', 'cosine', 'hamming', 'hann', 'tukey', 'lanczos', 'hilbert']

A class for sinogram filtering. It does the following:

• pad input array

• Fourier transform each row

• multiply with a 1D or 2D filter

• inverse Fourier transform

available_padding_modes = ['constant', 'edge', 'reflect', 'symmetric', 'wrap']

default_extra_options = {'cutoff': 1.0, 'fft_threads': 0}

set_filter(h_filt, normalize=True)

Set a filter for sinogram filtering.

Parameters:

• h_filt (numpy.ndarray) – Array containing the filter. Each line of the sinogram will be filtered with this filter. It has to be the Real-to-Complex Fourier Transform of some real filter, padded to 2*sinogram_width.

• normalize (bool or float, optional) – Whether to normalize (multiply) the filter with pi/num_angles.

filter_sino(sino, output=None, no_output=False)

Perform the sinogram siltering.

Parameters:

• sino (numpy.ndarray or pycuda.gpuarray.GPUArray) – Input sinogram (2D or 3D)

• output (numpy.ndarray or pycuda.gpuarray.GPUArray, optional) – Output array.

• no_output (bool, optional) – If set to True, no copy is be done. The resulting data lies in self.d_sino_padded.

nabu.reconstruction.filtering.filter_sinogram(sinogram, padded_width, filter_name='ramlak', padding_mode='constant', normalize=True, filter_cutoff=1.0, **padding_kwargs)

Simple function to filter sinogram.

Parameters:

• sinogram (numpy.ndarray) – Sinogram, two dimensional array with shape (n_angles, sino_width)

• padded_width (int) – Width to use for padding. Must be greater than sinogram width (i.e than sinogram.shape[-1])

• filter_name (str, optional) – Which filter to use. Default is ramlak (roughly equivalent to abs(nu) in frequency domain)

• padding_mode (str, optional) – Which padding mode to use. Default is zero-padding.

• normalize (bool, optional) – Whether to multiply the filtered sinogram with pi/n_angles

• filter_cutoff (float, optional) – frequency cutoff for filter