ifrt2

ifrt2

skimage.transform.ifrt2(a) [source]

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

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