def shift(x, wrg=0.1, hrg=0.1, is_random=False, row_index=0, col_index=1, channel_index=2,
fill_mode='nearest', cval=0.):
"""Shift an image randomly or non-randomly.
Parameters
-----------
x : numpy array
An image with dimension of [row, col, channel] (default).
wrg : float
Percentage of shift in axis x, usually -0.25 ~ 0.25.
hrg : float
Percentage of shift in axis y, usually -0.25 ~ 0.25.
is_random : boolean, default False
If True, randomly shift.
row_index, col_index, channel_index : int
Index of row, col and channel, default (0, 1, 2), for theano (1, 2, 0).
fill_mode : string
Method to fill missing pixel, default ‘nearest’, more options ‘constant’, ‘reflect’ or ‘wrap’.
- `scipy ndimage affine_transform <https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.ndimage.interpolation.affine_transform.html>`_
cval : scalar, optional
Value used for points outside the boundaries of the input if mode='constant'. Default is 0.0.
- `scipy ndimage affine_transform <https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.ndimage.interpolation.affine_transform.html>`_
"""
h, w = x.shape[row_index], x.shape[col_index]
if is_random:
tx = np.random.uniform(-hrg, hrg) * h
ty = np.random.uniform(-wrg, wrg) * w
else:
tx, ty = hrg * h, wrg * w
translation_matrix = np.array([[1, 0, tx],
[0, 1, ty],
[0, 0, 1]])
transform_matrix = translation_matrix # no need to do offset
x = apply_transform(x, transform_matrix, channel_index, fill_mode, cval)
return x
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