util.py

# 2021.01.27
# @yifan 
#
import numpy as np
from skimage.util import view_as_windows
from LANCZOS import LANCZOS

def Shrink(X, win):
    X = view_as_windows(X, (1,win,win,1), (1,win,win,1))
    return X.reshape(X.shape[0], X.shape[1], X.shape[2], -1)

def invShrink(X, win):
    S = X.shape
    X = X.reshape(S[0], S[1], S[2], -1, 1, win, win, 1)
    X = np.moveaxis(X, 5, 2)
    X = np.moveaxis(X, 6, 4)
    return X.reshape(S[0], win*S[1], win*S[2], -1)

def DownSample(X, r):
    a, b =  LANCZOS.split(X, r)   
    return a