:mod:`cddm.fft`
===============

.. py:module:: cddm.fft

.. autoapi-nested-parse::

   FFT tools.

   This module defines several functions for fft processing  of multi-frame data.



Module Contents
---------------

.. function:: rfft2_crop(x, kimax=None, kjmax=None)

   Crops rfft2 data.

   :param x: FFT2 data (as returned by np.rfft2 for instance). FFT2 must be over the
             last two axes.
   :type x: ndarray
   :param kimax: Max k value over the first (-2) axis of the FFT.
   :type kimax: int, optional
   :param kjmax: Max k value over the second (-1) axis of the FFT.
   :type kjmax: int, optional

   :returns: **out** -- Cropped fft array.
   :rtype: ndarray


.. function:: rfft2(video, kimax=None, kjmax=None, overwrite_x=False, extra={})

   A generator that performs rfft2 on a sequence of multi-frame data.

   Shape of the output depends on kimax and kjmax. It is (2*kimax+1, kjmax +1),
   or same as the result of rfft2 if kimax and kjmax are not defined.

   :param video: An iterable of multi-frame data
   :type video: iterable
   :param kimax: Max value of the wavenumber in vertical axis (i)
   :type kimax: int, optional
   :param kjmax: Max value of the wavenumber in horizontal axis (j)
   :type kjmax: int, optional
   :param overwrite_x: If input type is complex and fft library used is not numpy, fft can
                       be performed inplace to speed up computation.
   :type overwrite_x: bool, optional
   :param extra: Extra arguments passed to the underlying rfft2 cfunction. These arguments
                 are library dependent. For pyffyw see the documentation on
                 additional arguments for finer FFT control.
   :type extra: dict

   :returns: **video** -- An iterator over FFT of the video.
   :rtype: iterator


.. function:: normalize_fft(video, inplace=False, dtype=None)

   Normalizes each frame in fft video to the mean value (intensity) of
   the [0,0] component of fft.

   :param video: Input multi-frame iterable object. Each element of the iterable is a tuple
                 of ndarrays (frames)
   :type video: iterable
   :param inplace: Whether tranformation is performed inplace or not.
   :type inplace: bool, optional
   :param dtype: If specifed, determines output dtype. Only valid if inplace == False.
   :type dtype: numpy dtype

   :returns: **video** -- A multi-frame iterator
   :rtype: iterator