From 8226364eedc86e40afe7cc7d60dd74e1fb3e87fe Mon Sep 17 00:00:00 2001
From: Boyan <boyan@bobokara.com>
Date: Wed, 21 Jun 2023 17:26:37 +0300
Subject: [PATCH] Made NOAA decoder
---
src/classes/NOAADecoder.py | 65 ++++++++++++++++++++++++++++++++++++++
1 file changed, 65 insertions(+)
create mode 100644 src/classes/NOAADecoder.py
diff --git a/src/classes/NOAADecoder.py b/src/classes/NOAADecoder.py
new file mode 100644
index 0000000..acfb32e
--- /dev/null
+++ b/src/classes/NOAADecoder.py
@@ -0,0 +1,65 @@
+# Based on this article:
+# https://medium.com/swlh/decoding-noaa-satellite-images-using-50-lines-of-code-3c5d1d0a08da
+
+import scipy.io.wavfile as wav
+import scipy.signal as signal
+import numpy as np
+import matplotlib.pyplot as plt
+from PIL import Image
+from tqdm import tqdm
+
+class NOAADecoder:
+ def __init__(self, iq_data=None, filename=None) -> None:
+ # Check if iq_data or filename are set correctly
+ if iq_data and filename:
+ raise ValueError("Both iq_data and filename are set.")
+ if not iq_data and not filename:
+ raise ValueError("Neither iq_data nor filename are set.")
+
+ # Set iq_data or filename
+ if filename:
+ self.filename=filename
+ self.sample_rate, self.data = wav.read(f'{self.filename}')
+ if iq_data:
+ self.sample_rate = 2048000
+ self.data = self.iq_data
+
+ def hilbert(self, data):
+ # Hilbert transform
+ analytical_signal = signal.hilbert(data)
+ amplitude_envelope = np.abs(analytical_signal)
+ return amplitude_envelope
+
+ def decode(self, resample=4):
+
+ # Resample data
+ data = self.data[::resample]
+ sample_rate = self.sample_rate//resample
+
+ # Demodulate
+ data_am = self.hilbert(data)
+ frame_width = int(0.5*sample_rate)
+
+ # Image processing
+ w, h = frame_width, data_am.shape[0]//frame_width
+ image = Image.new('L', (w, h))
+ px, py = 0, 0
+
+ for p in tqdm(range(data_am.shape[0])):
+ if data_am[p][0] != data_am[p][1]:
+ raise BufferError("Mismatch in data array.")
+ lum = int(data_am[p][0]//32 - 32)
+ if lum < 0: lum = 0
+ if lum > 255: lum = 255
+ image.putpixel((px, py),lum)
+ px += 1
+ if px >= w:
+ px = 0
+ py += 1
+ if py >= h:
+ break
+ image = image.resize((w, 4*h))
+ plt.imshow(image, cmap='gray')
+ # Save image
+ image.save('noaa.png')
+ return
\ No newline at end of file