pyosv.freq.fft

 1#!/usr/bin/env python3
 2# -*- coding: utf-8 -*-
 3"""
 4Created on Tue Jun 28 17:50:18 2022
 5
 6@author: alessandrosebastianelli
 7"""
 8
 9import numpy as np
10
11def fft2d(image):
12    '''
13    
14        Calculates the 2D Fast Fourier Transform of an image
15        
16        Input:
17            - image: a WxH image, must be a single band image, with width W, height H
18        Outputs:
19            - fft: 2D spectrum of image
20    '''
21    
22    fft = np.fft.fftshift(np.fft.fft2(image))
23    
24    return fft
25
26def ifft2d(fft):
27    '''
28    
29        Calculates the inverse 2D Fast Fourier Transform of a spectrum of an image
30        
31        Input:
32            - fft: 2D spectrum of image 
33        Outputs:
34            - ifft: a WxH image
35    '''
36    
37    ifft = np.abs(np.fft.ifft2(np.fft.ifftshift(fft)))
38    
39    return ifft
40        
41def fft3d(image):
42    '''
43    
44        Calculates the 2D Fast Fourier Transform of an image with multiple bands
45        
46        Input:
47            - image: a WxHxB image, with width W, height H and B bands
48        Outputs:
49            - fft: array of 2D spectra of the image
50    '''
51    
52        
53    ffts = []    
54    for b in range(image.shape[-1]):
55        ffts.append(fft2d(image[:,:,b]))
56        
57    ffts = np.array(ffts)
58    ffts = np.moveaxis(ffts, 0, -1)
59        
60    return ffts 
61
62def ifft3d(ffts):
63    '''
64    
65        Calculates the inverse 2D Fast Fourier Transform of a vecctor of spectra of a multibands image
66        
67        Input:
68            - fft: array of 2D spectra of the image
69        Outputs:
70            - ifft: a WxHxB image, with width W, height H and B bands
71    '''
72        
73    iffts = []    
74    for b in range(ffts.shape[-1]):
75        iffts.append(ifft2d(ffts[:,:,b]))
76        
77    iffts = np.array(iffts)
78    iffts = np.moveaxis(iffts, 0, -1)
79        
80    return iffts