set_attenuation_coefficients¶
- sunkit_image.radial.set_attenuation_coefficients(order, range_mean=[1.0, 0.0], range_std=[1.0, 0.0], cutoff=0)[source]¶
This is a helper function to Fourier Normalizing Radial Gradient Filter (
sunkit_image.radial.fnrgf
).This function sets the attenuation coefficients in the one of the following two manners:
If
cutoff
is0
, then it will set the attenuation coefficients as linearly decreasing between the rangerange_mean
for the attenuation coefficents for mean approximation andrange_std
for the attenuation coefficients for standard deviation approximation.If
cutoff
is not0
, then it will set the lastcutoff
number of coefficients equal to zero while all the others the will be set as linearly decreasing as described above.Note
This function only describes some of the ways in which attenuation coefficients can be calculated. The optimal coefficients depends on the size and quality of image. There is no generalized formula for choosing them and its upto the user to choose a optimum value.
- Parameters:
order (
int
) – The order of the Fourier approximation.range_mean (
list
, optional) – A list of length of2
which contains the highest and lowest values between which the coefficients for mean approximation be calculated in a linearly decreasing manner.range_std (
list
, optional) – A list of length of2
which contains the highest and lowest values between which the coefficients for standard deviation approximation be calculated in a linearly decreasing manner.cutoff (
int
, optional) – The numbers of coefficients from the last that should be set tozero
.
- Returns:
numpy.ndarray
– A numpy array of shape[2, order + 1]
containing the attenuation coefficients for the Fourier coffiecients. The first row describes the attenustion coefficients for the Fourier coefficients of the mean approximation. The second row contains the attenuation coefficients for the Fourier coefficients of the standard deviation approximation.