downgrade_images.py

# -*- coding: utf-8 -*-
"""
Copyright (c) 2018 Image Processing Research Group of University Federico II of Naples ('GRIP-UNINA').
All rights reserved. This work should only be used for nonprofit purposes.
"""
import numpy as np
import scipy.ndimage as snd
import scipy.misc as misc
from others import gaussian2d, kaiser2d
from fir_filter_wind import fir_filter_wind

def downgrade_images(I_MS,I_PAN,ratio,sensor):
    """
    downgrade MS and PAN by a ratio factor with given sensor's gains
    """
    I_MS=np.double(I_MS)
    I_PAN=np.double(I_PAN)
    ratio=np.double(ratio)
    flag_PAN_MTF=0
    
    if sensor=='QB':
        flag_resize_new = 2
        GNyq = np.asarray([0.34, 0.32, 0.30, 0.22],dtype='float32')    # Band Order: B,G,R,NIR
        GNyqPan = 0.15
    elif sensor=='IKONOS':
        flag_resize_new = 2             #MTF usage
        GNyq = np.asarray([0.26,0.28,0.29,0.28],dtype='float32')    # Band Order: B,G,R,NIR
        GNyqPan = 0.17;
    elif sensor=='GeoEye1':
        flag_resize_new = 2             # MTF usage
        GNyq = np.asarray([0.23,0.23,0.23,0.23],dtype='float32')    # Band Order: B,G,R,NIR
        GNyqPan = 0.16     
    elif sensor=='WV2':
        flag_resize_new = 2             # MTF usage
        GNyq = [0.35,0.35,0.35,0.35,0.35,0.35,0.35,0.27]
        GNyqPan = 0.11
    elif sensor=='WV3':
        flag_resize_new = 2             #MTF usage
        GNyq = 0.29 * np.ones(8)
        GNyqPan = 0.15
    else:
        flag_resize_new = 1
        
    if flag_resize_new == 1:
        I_MS_LP = np.zeros((I_MS.shape[0],int(np.round(I_MS.shape[1]/ratio)+ratio),int(np.round(I_MS.shape[2]/ratio)+ratio)))
            
        for idim in xrange(I_MS.shape[0]):
            imslp_pad=np.pad(I_MS[idim,:,:],int(2*ratio),'symmetric')
            I_MS_LP[idim,:,:]=misc.imresize(imslp_pad,1/ratio,'bicubic',mode='F')
            
        I_MS_LR = I_MS_LP[:,2:-2,2:-2]
       
        I_PAN_pad=np.pad(I_PAN,int(2*ratio),'symmetric')
        I_PAN_LR=misc.imresize(I_PAN_pad,1/ratio,'bicubic',mode='F')
        I_PAN_LR=I_PAN_LR[2:-2,2:-2]
        
    elif flag_resize_new==2:
        
        N=41
        I_MS_LP=np.zeros(I_MS.shape)
        fcut=1/ratio
        
        for j in xrange(I_MS.shape[0]):
            #fir filter with window method
            alpha = np.sqrt(((N-1)*(fcut/2))**2/(-2*np.log(GNyq[j])))
            H=gaussian2d(N,alpha)
            Hd=H/np.max(H)
            w=kaiser2d(N,0.5)
            h=fir_filter_wind(Hd,w)
            I_MS_LP[j,:,:] = snd.filters.correlate(I_MS[j,:,:],np.real(h),mode='nearest')
        
        if flag_PAN_MTF==1:
            #fir filter with window method
            alpha = np.sqrt(((N-1)*(fcut/2))**2/(-2*np.log(GNyqPan)))
            H=gaussian2d(N,alpha)
            Hd=H/np.max(H)
            h=fir_filter_wind(Hd,w)
            I_PAN = snd.filters.correlate(I_PAN,np.real(h),mode='nearest')
            I_PAN_LR=I_PAN[int(ratio/2):-1:int(ratio),int(ratio/2):-1:int(ratio)]
            
        else:
            #bicubic resize
            I_PAN_pad=np.pad(I_PAN,int(2*ratio),'symmetric')
            I_PAN_LR=misc.imresize(I_PAN_pad,1/ratio,'bicubic',mode='F')
            I_PAN_LR=I_PAN_LR[2:-2,2:-2]
            
        I_MS_LR=I_MS_LP[:,int(ratio/2):-1:int(ratio),int(ratio/2):-1:int(ratio)]        
        
    return I_MS_LR,I_PAN_LR