Propose rotate function

gen_rotate.py

# -*- coding: utf-8 -*-
"""
:Created on: Tue Aug  7 16:44:50 2012

:author: Stuart Mumford

This is a wrapper for a general rotate method, it will rotate and rescale the
image around an arbitary point and then if requested shift the point to the centre.

"""

import numpy as np
import scipy.ndimage

def _af_args(angle, centre, shift, scale):
    """ Makes args for affine_transform scipy lib fun from values for
    input array, since fn. takes values in output array as args.  """

    # Re-usable bit - set centre, shift, ang
    c = np.cos(angle)
    s = np.sin(angle)
    mati = np.array([[c, s],[-s, c]])/scale   # res->orig
    centre = np.array([centre]).transpose()  # the centre of rotn
    shift = np.array([shift]).transpose()    # the shift
    kpos = centre - np.dot(mati, (centre + shift))  
    # kpos and mati are the two transform constants, kpos is a 2x1 array
    return (mati, (kpos[0,0], kpos[1,0]))

def rotate(image, angle, scale=1.0, centroid=None, recentre=True, order=3,
           missing=0.0, method='scipy'):
    """ Rotate, rescale and shift and image
    
    Arguments
    ---------
    image        ndarray         The input data
    angle        float           The angle to rotate the image by. (radians)
    
    Keyword Arguments
    -----------------
    scale       float           A scale factor for the image, default is no scaling
    centroid    tuple           The point in the image to rotate around (Axis of rotation),
                                default is the centre of the array
    recentre    bool, or list   Move the centroid (axis of rotation) to 
                                    the centre of the array or recentre coords
    order       int             The order of the spline interpolation to be used.
    missing     float           The numerical value of any missing data
    method      string          Selects the rotation method from:
                                    'scipy', 'C'
    """

    i_rows,i_cols = image.shape
    centre = ((i_rows - 1)/2.0, (i_cols - 1)/2.0)
    
    if not(centroid):
        centroid = centre
    
    if recentre:
        if centroid == centre:
            shift = (0., 0.)
        if type(recentre) in [list, tuple, np.ndarray]:
            shift = np.array(recentre) - np.array(centre)
        else:
            shift = np.array(centroid) - np.array(centre)
    else:
        shift = (0.,0.)
    
    if method == 'scipy':
        rsmat, offs = _af_args(angle, centroid, shift, scale)
        image.data = scipy.ndimage.interpolation.affine_transform(
            image, rsmat, offset=offs, order=order, mode='constant', cval=missing)
            
    elif method == 'C':
        raise NotImplementedError("Nope, not yet")
        
    else:
        if type(method) != type(''):
            raise TypeError("method keyword argument should be a string")
        raise ValueError("%s is not a valid argument for method"%method)
    
    return image
    
    

Two comments:
(1) I would suggest making radians optional, and make degrees the default. Most angles in FITS headers are quoted in degrees (I think), and I imagine this ability would be applied to FITS images quite directly.
(2) In which direction does the rotation operate - clockwise, or anti-clockwise?

Thanks!