`scipy.fftpack._realtransforms:idct`

source: /scipy/fftpack/_realtransforms.py :383

Signature

   def     idct (    x    ,    type    =  2   ,    n    =  None   ,    axis    =  -1   ,    norm    =  None   ,    overwrite_x    =  False     )

Summary

Return the Inverse Discrete Cosine Transform of an arbitrary type sequence.

Parameters

x : array_like: The input array.
type : {1, 2, 3, 4}, optional: Type of the DCT (see Notes). Default type is 2.
n : int, optional: Length of the transform. If n < x.shape[axis], x is truncated. If n > x.shape[axis], x is zero-padded. The default results in n = x.shape[axis].
axis : int, optional: Axis along which the idct is computed; the default is over the last axis (i.e., axis=-1).
norm : {None, 'ortho'}, optional: Normalization mode (see Notes). Default is None.
overwrite_x : bool, optional: If True, the contents of x can be destroyed; the default is False.

Returns

idct : ndarray of real: The transformed input array.

Notes

For a single dimension array x, idct(x, norm='ortho') is equal to MATLAB idct(x).

'The' IDCT is the IDCT of type 2, which is the same as DCT of type 3.

IDCT of type 1 is the DCT of type 1, IDCT of type 2 is the DCT of type 3, and IDCT of type 3 is the DCT of type 2. IDCT of type 4 is the DCT of type 4. For the definition of these types, see dct.

Examples

The Type 1 DCT is equivalent to the DFT for real, even-symmetrical inputs. The output is also real and even-symmetrical. Half of the IFFT input is used to generate half of the IFFT output:

from scipy.fftpack import ifft, idct
import numpy as np

✓

ifft(np.array([ 30.,  -8.,   6.,  -2.,   6.,  -8.])).real
idct(np.array([ 30.,  -8.,   6.,  -2.]), 1) / 6

✗

Aliases

scipy.fftpack.idct