def idct2(x, m, n):
"""
Apply the 2D Inverse Discrete Cosine Transform (iDCT) to `x`.
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
m : int
Number of rows in the associated matrix.
n : int
Number of columns in the associated matrix.
Returns
-------
ndarray
A m*n x 1 vector of coefficients scaled such that x = dct2(idct2(x)).
See Also
--------
scipy.fftpack.idct : 1D inverse DCT
"""
_validate_transform(x, m, n)
result = _vec2mat(x, (m, n))
result = scipy.fftpack.idct(result, norm='ortho').T
result = scipy.fftpack.idct(result, norm='ortho').T
return _mat2vec(result)
def idft2(x, m, n):
"""
Apply the 2D Inverse Discrete Fourier Transform (iDFT) to `x`.
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
m : int
Number of rows in the associated matrix.
n : int
Number of columns in the associated matrix.
Returns
-------
ndarray
A m*n x 1 vector of coefficients scaled such that x = idft2(dft2(x)).
See Also
--------
numpy.fft.ifft2 : The underlying 2D iFFT used to compute the 2D iDFT.
"""
_validate_transform(x, m, n)
output = _mat2vec(np.fft.ifft2(_vec2mat(x, (m, n))))
if np.abs(output.imag).sum() == 0:
output = output.real
return output
def dft2(x, m, n):
"""
Apply the 2D Discrete Fourier Transform (DFT) to `x`.
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
m : int
Number of rows in the associated matrix.
n : int
Number of columns in the associated matrix.
Returns
-------
ndarray
A m*n x 1 vector of coefficients scaled such that x = dft2(idft2(x)).
See Also
--------
numpy.fft.fft2 : The underlying 2D FFT used to compute the 2D DFT.
"""
_validate_transform(x, m, n)
return _mat2vec(np.fft.fft2(_vec2mat(x, (m, n))))
def dct2(x, mn_tuple, overcomplete_mn_tuple=None):
"""
Apply the 2D Discrete Cosine Transform (DCT).
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
mn_tuple : tuple of int
`(m, n)` - `m` number of rows in the matrix represented by `x`; `n`
number of columns in the matrix.
overcomplete_mn_tuple : tuple of int, optional
`(mo, no)` - `mo` number of rows in the matrix represented by the
function's output; `no` number of columns in the matrix.
Returns
-------
alpha : ndarray
When `overcomplete_mn_tuple` is omitted: an m*n x 1 vector of
coefficients scaled such that x = idct2(dct2(x)). When
`overcomplete_mn_tuple` is supplied: an mo*no x 1 vector of
coefficients scaled such that x = idct2(dct2(x)).
See Also
--------
scipy.fftpack.dct : 1D DCT
Notes
-----
The overcomplete transform feature invoked by supplying
`overcomplete_mn_tuple` is only available for SciPy >= 0.16.1.
The 2D DCT uses the seperability property of the 1D DCT.
http://stackoverflow.com/questions/14325795/scipys-fftpack-dct-and-idct
Including the reshape operation, the full transform is:
dct(dct(x.reshape(n, m).T).T).T.T.reshape(m * n, 1)
"""
@_decorate_validation
def validate_input():
_validate_transform_fwd(x, mn_tuple, overcomplete_mn_tuple)
validate_input()
m, n = mn_tuple
result = _vec2mat(x, (m, n))
if overcomplete_mn_tuple is None:
result = scipy.fftpack.dct(result, norm='ortho').T
result = scipy.fftpack.dct(result, norm='ortho').T
else:
mo, no = overcomplete_mn_tuple
result = scipy.fftpack.dct(result, norm='ortho', n=no).T
result = scipy.fftpack.dct(result, norm='ortho', n=mo).T
return _mat2vec(result)
def idct2(x, mn_tuple, overcomplete_mn_tuple=None):
"""
Apply the 2D Inverse Discrete Cosine Transform (iDCT).
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The vector representing the associated column-stacked matrix. When
`overcomplete_mn_tuple` is omitted: the shape must be m*n x 1. When
`overcomplete_mn_tuple` is supplied: the shape must be mo*no x 1.
mn_tuple : tuple of int
`(m, n)` - `m` number of rows in the associated matrix, `n` number of
columns in the associated matrix. When `overcomplete_mn_tuple` is
supplied, this is the shape of the function's output.
overcomplete_mn_tuple : tuple of int, optional
`(mo, no)` - `mo` number of rows in the associated matrix, `no` number
of columns in the associated matrix. When supplied, this is the shape
of the function's input.
Returns
-------
ndarray
An m*n x 1 vector of coefficients scaled such that x = dct2(idct2(x)).
See Also
--------
scipy.fftpack.idct : 1D inverse DCT
Notes
-----
The overcomplete transform feature invoked by supplying
`overcomplete_mn_tuple` is only available for SciPy >= 0.16.1.
"""
@_decorate_validation
def validate_input():
_validate_transform_bwd(x, mn_tuple, overcomplete_mn_tuple)
validate_input()
m, n = mn_tuple
if overcomplete_mn_tuple is None:
result = _vec2mat(x, (m, n))
result = scipy.fftpack.idct(result, norm='ortho').T
result = scipy.fftpack.idct(result, norm='ortho').T
else:
mo, no = overcomplete_mn_tuple
result = _vec2mat(x, (mo, no))
result = scipy.fftpack.idct(result, norm='ortho').T
result = result[:n, :]
result = scipy.fftpack.idct(result, norm='ortho').T
result = result[:m, :]
return _mat2vec(result)
def idft2(x, mn_tuple, overcomplete_mn_tuple=None):
"""
Apply the 2D Inverse Discrete Fourier Transform (iDFT).
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
mn_tuple : tuple of int
`(m, n)` - `m` number of rows in the associated matrix, `n` number of
columns in the associated matrix. When `overcomplete_mn_tuple`
is supplied, this is the shape of the function's output.
overcomplete_mn_tuple : tuple of int, optional
`(mo, no)` - `mo` number of rows in the associated matrix, `no` number
of columns in the associated matrix. When supplied, this is the shape
of the function's input.
Returns
-------
ndarray
An m*n x 1 vector of coefficients scaled such that x = dft2(idft2(x)).
See Also
--------
numpy.fft.ifft2 : The underlying 2D iFFT used to compute the 2D iDFT.
Notes
-----
This is a normalised iDFT, i.e. a normalisation constant of
:math:`\sqrt{m * n}` is used.
"""
@_decorate_validation
def validate_input():
_validate_transform_bwd(x, mn_tuple, overcomplete_mn_tuple)
validate_input()
m, n = mn_tuple
if overcomplete_mn_tuple is None:
result = _vec2mat(x, (m, n))
result = np.sqrt(n * m) * np.fft.ifft2(result)
else:
mo, no = overcomplete_mn_tuple
result = _vec2mat(x, (mo, no))
result = np.sqrt(no * mo) * np.fft.ifft2(result)
result = result[:m, :n]
if np.allclose(result.imag, 0):
result = result.real
return _mat2vec(result)
def dft2(x, mn_tuple, overcomplete_mn_tuple=None):
"""
Apply the 2D Discrete Fourier Transform (DFT).
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
mn_tuple : tuple of int
`(m, n)` - `m` number of rows in the matrix represented by `x`; `n`
number of columns in the matrix.
overcomplete_mn_tuple : tuple of int, optional
`(mo, no)` - `mo` number of rows in the matrix represented by the
function's output; `no` number of columns in the matrix.
Returns
-------
ndarray
When `overcomplete_mn_tuple` is omitted: an m*n x 1 vector of
coefficients scaled such that x = idft2(dft2(x)). When
`overcomplete_mn_tuple` is supplied: an mo*no x 1 vector of
coefficients scaled such that x = idft2(dft2(x)).
See Also
--------
numpy.fft.fft2 : The underlying 2D FFT used to compute the 2D DFT.
Notes
-----
This is a normalised DFT, i.e. a normalisation constant of
:math:`\sqrt{m * n}` is used.
"""
@_decorate_validation
def validate_input():
_validate_transform_fwd(x, mn_tuple, overcomplete_mn_tuple)
validate_input()
m, n = mn_tuple
result = _vec2mat(x, (m, n))
if overcomplete_mn_tuple is None:
result = 1 / np.sqrt(n * m) * np.fft.fft2(result)
else:
mo, no = overcomplete_mn_tuple
result = 1 / np.sqrt(no * mo) * np.fft.fft2(result, s=(mo, no))
return _mat2vec(result)
def dct2(x, mn_tuple):
"""
Apply the 2D Discrete Cosine Transform (DCT) to `x`.
`x` is assumed to be the column vector resulting from stacking the columns
of the associated matrix which the transform is to be taken on.
Parameters
----------
x : ndarray
The m*n x 1 vector representing the associated column stacked matrix.
m : int
Number of rows in the associated matrix.
n : int
Number of columns in the associated matrix.
Returns
-------
ndarray
A m*n x 1 vector of coefficients scaled such that x = idct2(dct2(x)).
See Also
--------
scipy.fftpack.dct : 1D DCT
"""
m, n = mn_tuple
@_decorate_validation
def validate_input():
_validate_transform(x, m, n)
validate_input()
# 2D DCT using the seperability property of the 1D DCT.
# http://stackoverflow.com/questions/14325795/scipys-fftpack-dct-and-idct
# Including the reshape operation, the full transform is:
# dct(dct(x.reshape(n, m).T).T).T.T.reshape(m * n, 1)
result = _vec2mat(x, (m, n))
result = scipy.fftpack.dct(result, norm='ortho').T
result = scipy.fftpack.dct(result, norm='ortho').T
return _mat2vec(result)
