ifrt2
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skimage.transform.ifrt2(a)
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Compute the 2-dimensional inverse finite radon transform (iFRT) for an (n+1) x n integer array.
Parameters: a : array_like
A 2-D (n+1) row x n column integer array.
Returns: iFRT : 2-D n x n ndarray
Inverse Finite Radon Transform array of n x n integer coefficients.
See also
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frt2
- The two-dimensional FRT
Notes
The FRT has a unique inverse if and only if n is prime. See [R368] for an overview. The idea for this algorithm is due to Vlad Negnevitski.
References
[R368] (1, 2) A. Kingston and I. Svalbe, “Projective transforms on periodic discrete image arrays,” in P. Hawkes (Ed), Advances in Imaging and Electron Physics, 139 (2006) Examples
>>> SIZE = 59 >>> img = np.tri(SIZE, dtype=np.int32)
Apply the Finite Radon Transform:
>>> f = frt2(img)
Apply the Inverse Finite Radon Transform to recover the input
>>> fi = ifrt2(f)
Check that it’s identical to the original
>>> assert len(np.nonzero(img-fi)[0]) == 0
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