augment.py 文件源码

def build_rescale_transform_slow(downscale_factor, image_shape, target_shape):
    """
    This mimics the skimage.transform.resize function.
    The resulting image is centered.
    """
    rows, cols = image_shape
    trows, tcols = target_shape
    col_scale = row_scale = downscale_factor
    src_corners = np.array([[1, 1], [1, rows], [cols, rows]]) - 1
    dst_corners = np.zeros(src_corners.shape, dtype=np.double)
    # take into account that 0th pixel is at position (0.5, 0.5)
    dst_corners[:, 0] = col_scale * (src_corners[:, 0] + 0.5) - 0.5
    dst_corners[:, 1] = row_scale * (src_corners[:, 1] + 0.5) - 0.5

    tform_ds = skimage.transform.AffineTransform()
    tform_ds.estimate(src_corners, dst_corners)

    # centering    
    shift_x = cols / (2.0 * downscale_factor) - tcols / 2.0
    shift_y = rows / (2.0 * downscale_factor) - trows / 2.0
    tform_shift_ds = skimage.transform.SimilarityTransform(translation=(shift_x, shift_y))
    return tform_shift_ds + tform_ds