prepro.py 文件源码

def swirl(x, center=None, strength=1, radius=100, rotation=0, output_shape=None, order=1, mode='constant', cval=0, clip=True, preserve_range=False, is_random=False):
    """Swirl an image randomly or non-randomly, see `scikit-image swirl API <http://scikit-image.org/docs/dev/api/skimage.transform.html#skimage.transform.swirl>`_
    and `example <http://scikit-image.org/docs/dev/auto_examples/plot_swirl.html>`_.

    Parameters
    -----------
    x : numpy array
        An image with dimension of [row, col, channel] (default).
    center : (row, column) tuple or (2,) ndarray, optional
        Center coordinate of transformation.
    strength : float, optional
        The amount of swirling applied.
    radius : float, optional
        The extent of the swirl in pixels. The effect dies out rapidly beyond radius.
    rotation : float, (degree) optional
        Additional rotation applied to the image, usually [0, 360], relates to center.
    output_shape : tuple (rows, cols), optional
        Shape of the output image generated. By default the shape of the input image is preserved.
    order : int, optional
        The order of the spline interpolation, default is 1. The order has to be in the range 0-5. See skimage.transform.warp for detail.
    mode : {‘constant’, ‘edge’, ‘symmetric’, ‘reflect’, ‘wrap’}, optional
        Points outside the boundaries of the input are filled according to the given mode, with ‘constant’ used as the default. Modes match the behaviour of numpy.pad.
    cval : float, optional
        Used in conjunction with mode ‘constant’, the value outside the image boundaries.
    clip : bool, optional
        Whether to clip the output to the range of values of the input image. This is enabled by default, since higher order interpolation may produce values outside the given input range.
    preserve_range : bool, optional
        Whether to keep the original range of values. Otherwise, the input image is converted according to the conventions of img_as_float.
    is_random : boolean, default False
        If True, random swirl.
            - random center = [(0 ~ x.shape[0]), (0 ~ x.shape[1])]
            - random strength = [0, strength]
            - random radius = [1e-10, radius]
            - random rotation = [-rotation, rotation]

    Examples
    ---------
    >>> x --> [row, col, 1] greyscale
    >>> x = swirl(x, strength=4, radius=100)
    """
    assert radius != 0, Exception("Invalid radius value")
    rotation = np.pi / 180 * rotation
    if is_random:
        center_h = int(np.random.uniform(0, x.shape[0]))
        center_w = int(np.random.uniform(0, x.shape[1]))
        center = (center_h, center_w)
        strength = np.random.uniform(0, strength)
        radius = np.random.uniform(1e-10, radius)
        rotation = np.random.uniform(-rotation, rotation)

    max_v = np.max(x)
    if max_v > 1:   # Note: the input of this fn should be [-1, 1], rescale is required.
        x = x / max_v
    swirled = skimage.transform.swirl(x, center=center, strength=strength, radius=radius, rotation=rotation,
        output_shape=output_shape, order=order, mode=mode, cval=cval, clip=clip, preserve_range=preserve_range)
    if max_v > 1:
        swirled = swirled * max_v
    return swirled