From f9f3ad0712593b46bb81ba3c6dedadfd82b48e0d Mon Sep 17 00:00:00 2001
From: Abdussalam SALEH MGHIR <salehma@visu01.sis.cnes.fr>
Date: Mon, 27 Sep 2021 07:42:43 +0000
Subject: [PATCH] ENH : Python script to compute average spectra in range and
in azimuth for a Tiff image
---
python_src/utils/compute_spectra_ImageTiff.py | 109 ++++++++++++++++++
1 file changed, 109 insertions(+)
create mode 100755 python_src/utils/compute_spectra_ImageTiff.py
diff --git a/python_src/utils/compute_spectra_ImageTiff.py b/python_src/utils/compute_spectra_ImageTiff.py
new file mode 100755
index 0000000..fb04409
--- /dev/null
+++ b/python_src/utils/compute_spectra_ImageTiff.py
@@ -0,0 +1,109 @@
+# coding:utf-8
+import sys
+import numpy as np
+import matplotlib.pyplot as plt
+import os
+import argparse
+try:
+ import gdal
+except ImportError:
+ import osgeo.gdal as gdal
+def calcul_spectres_tiff(ficima,output_path, output_filename_az, output_filename_dist):
+ """
+ Compute the average spectra in range and in azimuth from a complex SAR image (mandatory format .tif)
+ """
+ # Average spectrum in azimut
+ ###################################
+
+ print("Compute the average spectrum in azimut after loading the modules python and gdal")
+ #Read the image tiff
+ zone = read_tiff(ficima)
+ print ("Dimensions of the tif file ",np.shape(zone))
+ (nb_lig, nb_col) = np.shape(zone[:,:,0])
+ print ("nb lig = ",nb_lig," nb col = ", nb_col)
+
+ lig = np.zeros(nb_lig, dtype = complex)
+ spectre_az = np.zeros(nb_lig, dtype = 'float')
+
+ for i in range(nb_col):
+ lig = zone[:,i,0] + 1j*zone[:,i,1] #All the lines in complex
+ spectre_az = spectre_az + np.abs(np.fft.fft(lig))**2
+
+ spectre_az = np.sqrt(spectre_az) / float(nb_col)
+
+ #Display and Save the spectrum
+ display_spectrum(spectre_az, "Average spectrum in azimut", output_path, output_filename_az)
+
+ # Compute the average spectrum in range
+ #####################################
+
+ print("Compute the average spectrum in range")
+ col = np.zeros(nb_col, dtype = complex)
+ spectre_dist = np.zeros(nb_col, dtype = 'float')
+
+ for i in range(nb_lig):
+ col = zone[i,:,0] + 1j*zone[i,:,1] #All the columns in complex
+ spectre_dist = spectre_dist + np.abs(np.fft.fft(col))**2
+
+ spectre_dist = np.sqrt(spectre_dist) / float(nb_lig)
+
+ #Display and Save the spectrum
+ print("Display and Save the spectrum")
+ display_spectrum(spectre_dist, "Average spectrum in range", output_path, output_filename_dist)
+
+ plt.show()
+
+def read_tiff(filename):
+ """
+ Create a numpy array from the input image tiff.
+ """
+ ds = gdal.Open(filename)
+
+ nb_lig = ds.RasterYSize
+ nb_col = ds.RasterXSize
+ nb_bands = ds.RasterCount
+
+ zone = np.zeros((nb_lig, nb_col, nb_bands))
+
+ for i in range(nb_bands):
+ zone[:,:,i] = np.array(ds.GetRasterBand(i+1).ReadAsArray())
+
+ return zone
+
+def display_spectrum(spectre, title, path, filename):
+ """
+ Display the normalized spectrum.
+ """
+ nb_val = np.size(spectre)
+ xvals = np.arange(nb_val) / float(nb_val)
+
+ plt.figure()
+ plt.plot(xvals, spectre)
+ plt.ylim(0, 1.1*max(spectre))
+ plt.title(title + "\n" + filename)
+ plt.savefig(os.path.join(path,filename))
+ plt.draw()
+
+
+if __name__ == "__main__":
+ description = "Compute of the spectra of the image tif"
+ parser = argparse.ArgumentParser(description=description)
+ parser.add_argument("path_input", type=str, help="Path of the input Tiff Image to get its spectrum. There is not its extension in the path")
+ parser.add_argument("path_output_dir", type=str, help="Path of the output directory where the spectra of the input will be saved")
+ args = parser.parse_args()
+
+
+ print("Usage : python compute_spectra_ImageTiff.py <path_input_tif_image without the extension file> <path_output_directory>")
+ print("The Tiff Image must have 2 bands in float/int. The script cannot read the image with one band in complex")
+ path_input = args.path_input
+ file_input = path_input.split('/')[-1]
+ input_path = os.path.dirname(path_input)
+ if(input_path==''):
+ input_path = '.'
+ nomima = file_input.split('.')[0]
+ ficima=os.path.join(input_path,nomima+".tif")
+ output_path=args.path_output_dir
+ output_filename_az="spectrum_az_"+nomima
+ output_filename_dist="spectrum_dist_"+nomima
+
+ calcul_spectres_tiff(ficima,output_path, output_filename_az, output_filename_dist)
--
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