[Scipy-svn] r5453 - trunk/scipy/fftpack

[scipy-svn at scipy.org]

Author: cdavid
Date: 2009-01-12 20:02:23 -0600 (Mon, 12 Jan 2009)
New Revision: 5453

Added:
   trunk/scipy/fftpack/realtransforms.py
Log:
Add python wrapper around fftpack dct.

Added: trunk/scipy/fftpack/realtransforms.py
===================================================================
--- trunk/scipy/fftpack/realtransforms.py	2009-01-13 02:01:59 UTC (rev 5452)
+++ trunk/scipy/fftpack/realtransforms.py	2009-01-13 02:02:23 UTC (rev 5453)
@@ -0,0 +1,91 @@
+"""
+Real spectrum tranforms (DCT, DST, MDCT)
+"""
+
+__all__ = ['dct1', 'dct2']
+
+import numpy as np
+from scipy.fftpack import _fftpack
+
+import atexit
+atexit.register(_fftpack.destroy_dct1_cache)
+atexit.register(_fftpack.destroy_dct2_cache)
+
+def dct1(x, n=None):
+    """
+    Return Discrete Cosine Transform (type I) of arbitrary type sequence x.
+
+    Parameters
+    ----------
+    x : array-like
+        input array.
+    n : int, optional
+        Length of the transform.
+
+    Returns
+    -------
+    y : real ndarray
+    """
+    return _dct(x, 1, n)
+
+def dct2(x, n=None):
+    """
+    Return Discrete Cosine Transform (type II) of arbitrary type sequence x.
+
+    Parameters
+    ----------
+    x : array-like
+        input array.
+    n : int, optional
+        Length of the transform.
+
+    Returns
+    -------
+    y : real ndarray
+    """
+    return _dct(x, 2, n)
+
+def _dct(x, type, n=None, axis=-1, overwrite_x=0):
+    """
+    Return Discrete Cosine Transform of arbitrary type sequence x.
+
+    Parameters
+    ----------
+    x : array-like
+        input array.
+    n : int, optional
+        Length of the transform.
+    axis : int, optional
+        Axis along which the dct is computed. (default=-1)
+    overwrite_x : bool, optional
+        If True the contents of x can be destroyed. (default=False)
+
+    Returns
+    -------
+    z : real ndarray
+
+    """
+    tmp = np.asarray(x)
+    if not np.isrealobj(tmp):
+        raise TypeError,"1st argument must be real sequence"
+
+    if n is None:
+        n = tmp.shape[axis]
+    else:
+        raise NotImplemented("Padding/truncating not yet implemented")
+
+    if type == 1:
+        f = _fftpack.dct1
+    elif type == 2:
+        f = _fftpack.dct2
+    else:
+        raise ValueError("Type %d not understood" % type)
+
+    if axis == -1 or axis == len(tmp.shape) - 1:
+        return f(tmp, n, 0, overwrite_x)
+    else:
+        raise NotImplementedError("Axis arg not yet implemented")
+
+    #tmp = swapaxes(tmp, axis, -1)
+    #tmp = work_function(tmp,n,1,0,overwrite_x)
+    #return swapaxes(tmp, axis, -1)