For a single dimension array x, idct(x, norm='ortho')
is equal to MATLAB idct(x)
.
correspondence with the inverse direct Fourier transform. To recover it you must specify orthogonalize=False
.
For norm="ortho"
both the dct
and idct
are scaled by the same overall factor in both directions. By default, the transform is also orthogonalized which for types 1, 2 and 3 means the transform definition is modified to give orthogonality of the IDCT matrix (see dct
for the full definitions).
'The' IDCT is the IDCT-II, which is the same as the normalized DCT-III.
The IDCT is equivalent to a normal DCT except for the normalization and type. DCT type 1 and 4 are their own inverse and DCTs 2 and 3 are each other's inverses.
The input array.
Type of the DCT (see Notes). Default type is 2.
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 along which the idct is computed; the default is over the last axis (i.e., axis=-1
).
Normalization mode (see Notes). Default is "backward".
If True, the contents of x can be destroyed; the default is False.
Maximum number of workers to use for parallel computation. If negative, the value wraps around from os.cpu_count()
. See ~scipy.fft.fft
for more details.
Whether to use the orthogonalized IDCT variant (see Notes). Defaults to True
when norm=="ortho"
and False
otherwise.
The transformed input array.
Return the Inverse Discrete Cosine Transform of an arbitrary type sequence.
dct
Forward DCT
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.fft import ifft, idct
... ifft(np.array([ 30., -8., 6., -2., 6., -8.])).real array([ 4., 3., 5., 10., 5., 3.])
>>> idct(np.array([ 30., -8., 6., -2.]), 1) array([ 4., 3., 5., 10.])See :
The following pages refer to to this document either explicitly or contain code examples using this.
scipy.fft._realtransforms.dct
scipy.fft._realtransforms.idctn
scipy.fft._realtransforms.idct
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