new background remove algoritm

tests/test_background_buffer.py

@@ -0,0 +1,44 @@
+from __future__ import annotations
+
+import numpy as np
+import unittest
+
+from rfg_adc_plotter.state.background_buffer import BackgroundMedianBuffer
+
+
+class BackgroundMedianBufferTests(unittest.TestCase):
+    def test_buffer_returns_median_for_partial_fill(self):
+        buffer = BackgroundMedianBuffer(max_rows=4)
+        buffer.push(np.asarray([1.0, 5.0, 9.0], dtype=np.float32))
+        buffer.push(np.asarray([3.0, 7.0, 11.0], dtype=np.float32))
+
+        median = buffer.median()
+
+        self.assertIsNotNone(median)
+        self.assertTrue(np.allclose(median, np.asarray([2.0, 6.0, 10.0], dtype=np.float32)))
+
+    def test_buffer_wraparound_keeps_latest_rows(self):
+        buffer = BackgroundMedianBuffer(max_rows=2)
+        buffer.push(np.asarray([1.0, 5.0], dtype=np.float32))
+        buffer.push(np.asarray([3.0, 7.0], dtype=np.float32))
+        buffer.push(np.asarray([9.0, 11.0], dtype=np.float32))
+
+        median = buffer.median()
+
+        self.assertIsNotNone(median)
+        self.assertTrue(np.allclose(median, np.asarray([6.0, 9.0], dtype=np.float32)))
+
+    def test_buffer_reset_clears_state(self):
+        buffer = BackgroundMedianBuffer(max_rows=2)
+        buffer.push(np.asarray([1.0, 2.0], dtype=np.float32))
+
+        buffer.reset()
+
+        self.assertIsNone(buffer.rows)
+        self.assertIsNone(buffer.median())
+        self.assertEqual(buffer.count, 0)
+        self.assertEqual(buffer.head, 0)
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_processing.py

@@ -14,6 +14,11 @@ from rfg_adc_plotter.processing.calibration import (
     recalculate_calibration_c,
     save_calib_envelope,
 )
+from rfg_adc_plotter.processing.background import (
+    load_fft_background,
+    save_fft_background,
+    subtract_fft_background,
+)
 from rfg_adc_plotter.processing.fft import (
     build_positive_only_centered_ifft_spectrum,
     build_symmetric_ifft_spectrum,
@@ -101,6 +106,28 @@ class ProcessingTests(unittest.TestCase):
             with self.assertRaises(ValueError):
                 load_calib_envelope(path)
 
+    def test_fft_background_roundtrip_and_rejects_non_1d_payload(self):
+        background = np.asarray([0.5, 1.5, 2.5], dtype=np.float32)
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            path = os.path.join(tmp_dir, "fft_background")
+            saved_path = save_fft_background(path, background)
+            loaded = load_fft_background(saved_path)
+            self.assertTrue(saved_path.endswith(".npy"))
+            self.assertTrue(np.allclose(loaded, background))
+
+            invalid_path = os.path.join(tmp_dir, "fft_background_invalid.npy")
+            np.save(invalid_path, np.zeros((2, 2), dtype=np.float32))
+            with self.assertRaises(ValueError):
+                load_fft_background(invalid_path)
+
+    def test_subtract_fft_background_clamps_negative_residuals_to_zero(self):
+        signal = np.asarray([1.0, 2.0, 3.0], dtype=np.float32)
+        background = np.asarray([1.0, 1.5, 5.0], dtype=np.float32)
+        subtracted = subtract_fft_background(signal, background)
+
+        self.assertTrue(np.allclose(subtracted, np.asarray([0.0, 0.5, 0.0], dtype=np.float32)))
+        self.assertTrue(np.allclose(subtract_fft_background(signal, signal), 0.0))
+
     def test_apply_working_range_crops_sweep_to_selected_band(self):
         freqs = np.linspace(3.3, 14.3, 12, dtype=np.float64)
         sweep = np.arange(12, dtype=np.float32)

tests/test_ring_buffer.py

@@ -15,6 +15,7 @@ class RingBufferTests(unittest.TestCase):
         self.assertIsNotNone(ring.ring_fft)
         self.assertIsNotNone(ring.ring_time)
         self.assertIsNotNone(ring.distance_axis)
+        self.assertIsNotNone(ring.get_last_fft_linear())
         self.assertIsNotNone(ring.last_fft_db)
         self.assertEqual(ring.ring.shape[0], 4)
         self.assertEqual(ring.ring_fft.shape, (4, ring.fft_bins))
@@ -52,6 +53,7 @@ class RingBufferTests(unittest.TestCase):
         self.assertTrue(changed)
         self.assertFalse(ring.fft_symmetric)
         self.assertEqual(ring.get_display_raw().shape[1], 2)
+        self.assertIsNotNone(ring.get_last_fft_linear())
         self.assertEqual(ring.last_fft_db.shape, fft_before.shape)
         self.assertFalse(np.allclose(ring.last_fft_db, fft_before))
         self.assertFalse(np.allclose(ring.distance_axis, axis_before))