i.fft: added test file for i.fft module (#4931)

imagery/i.fft/testsuite/test_i_fft.py

@@ -0,0 +1,216 @@
+import numpy as np
+from grass.script import array
+from grass.gunittest.case import TestCase
+from grass.gunittest.main import test
+
+
+class TestIFFT(TestCase):
+    """Regression tests for the i.fft GRASS GIS module."""
+
+    input_raster = "test_input"
+    real_output = "fft_real"
+    imag_output = "fft_imag"
+
+    @classmethod
+    def setUpClass(cls):
+        """Set up an input raster and configure test environment."""
+        cls.use_temp_region()
+        cls.runModule("g.region", n=10, s=0, e=10, w=0, rows=10, cols=10)
+        cls.runModule(
+            "r.mapcalc", expression=f"{cls.input_raster} = col()", overwrite=True
+        )
+
+    @classmethod
+    def tearDownClass(cls):
+        """Clean up generated data and reset the region."""
+        rasters_to_remove = [
+            cls.input_raster,
+            cls.real_output,
+            cls.imag_output,
+            "reconstructed",
+            "input_2",
+            "combined",
+            "real_1",
+            "imag_1",
+            "real_2",
+            "imag_2",
+            "combined_real",
+            "combined_imag",
+        ]
+        cls.runModule(
+            "g.remove",
+            type="raster",
+            name=",".join(rasters_to_remove),
+            flags="f",
+            quiet=True,
+        )
+        cls.del_temp_region()
+
+    def test_linearity_property(self):
+        """Test linearity of the FFT by combining two rasters."""
+        self.runModule("r.mapcalc", expression="input_2 = row()", overwrite=True)
+        self.runModule(
+            "r.mapcalc", expression="combined = test_input + input_2", overwrite=True
+        )
+
+        self.assertModule(
+            "i.fft",
+            input=self.input_raster,
+            real="real_1",
+            imaginary="imag_1",
+            overwrite=True,
+        )
+        self.assertRasterExists("real_1")
+        self.assertRasterExists("imag_1")
+
+        self.assertModule(
+            "i.fft", input="input_2", real="real_2", imaginary="imag_2", overwrite=True
+        )
+        self.assertRasterExists("real_2")
+        self.assertRasterExists("imag_2")
+
+        self.assertModule(
+            "i.fft",
+            input="combined",
+            real="combined_real",
+            imaginary="combined_imag",
+            overwrite=True,
+        )
+
+        self.assertRasterExists("combined_real")
+        self.assertRasterExists("combined_imag")
+
+        real_combined = array.array("combined_real")
+        imag_combined = array.array("combined_imag")
+        real_sum = array.array("real_1") + array.array("real_2")
+        imag_sum = array.array("imag_1") + array.array("imag_2")
+
+        self.assertTrue(
+            np.allclose(real_combined, real_sum, atol=1e-5),
+            "Linearity failed for real component",
+        )
+        self.assertTrue(
+            np.allclose(imag_combined, imag_sum, atol=1e-5),
+            "Linearity failed for imaginary component",
+        )
+
+    def test_energy_conservation_theorem(self):
+        """Validate energy conservation theorem."""
+        self.assertModule(
+            "i.fft",
+            input=self.input_raster,
+            real=self.real_output,
+            imaginary=self.imag_output,
+            overwrite=True,
+        )
+
+        self.assertRasterExists(self.real_output)
+        self.assertRasterExists(self.imag_output)
+
+        spatial_energy = np.sum(array.array(self.input_raster) ** 2)
+        freq_energy = np.sum(
+            array.array(self.real_output) ** 2 + array.array(self.imag_output) ** 2
+        )
+        self.assertAlmostEqual(
+            spatial_energy, freq_energy, places=5, msg="Energy conservation failed"
+        )
+
+    def test_inverse_fft(self):
+        """Check that inverse FFT reconstructs the original raster."""
+        self.assertModule(
+            "i.fft",
+            input=self.input_raster,
+            real=self.real_output,
+            imaginary=self.imag_output,
+            overwrite=True,
+        )
+
+        self.assertRasterExists(self.real_output)
+        self.assertRasterExists(self.imag_output)
+
+        self.assertModule(
+            "i.ifft",
+            real=self.real_output,
+            imaginary=self.imag_output,
+            output="reconstructed",
+            overwrite=True,
+        )
+
+        original_values = array.array(self.input_raster)
+        reconstructed_values = array.array("reconstructed")
+
+        self.assertTrue(
+            np.allclose(original_values, reconstructed_values, atol=1e-5),
+            "Reconstructed raster does not match the original",
+        )
+
+    def test_all_zero_raster(self):
+        """Test FFT behavior with an all-zero raster."""
+        self.runModule(
+            "r.mapcalc", expression=f"{self.input_raster} = 0", overwrite=True
+        )
+        self.assertModule(
+            "i.fft",
+            input=self.input_raster,
+            real=self.real_output,
+            imaginary=self.imag_output,
+            overwrite=True,
+        )
+        self.assertRasterExists(self.real_output)
+        self.assertRasterExists(self.imag_output)
+
+        real_values = array.array(self.real_output)
+        imag_values = array.array(self.imag_output)
+        self.assertTrue(
+            np.allclose(real_values, 0), "Real component should be all zeros"
+        )
+        self.assertTrue(
+            np.allclose(imag_values, 0), "Imaginary component should be all zeros"
+        )
+
+    def test_all_one_raster(self):
+        """Test FFT behavior with an all-one raster."""
+        self.runModule(
+            "r.mapcalc", expression=f"{self.input_raster} = 1", overwrite=True
+        )
+        self.assertModule(
+            "i.fft",
+            input=self.input_raster,
+            real=self.real_output,
+            imaginary=self.imag_output,
+            overwrite=True,
+        )
+        self.assertRasterExists(self.real_output)
+        self.assertRasterExists(self.imag_output)
+
+        real_values = array.array(self.real_output)
+        imag_values = array.array(self.imag_output)
+        self.assertTrue(
+            np.all(np.isfinite(real_values)), "Real component should have valid values"
+        )
+        self.assertTrue(
+            np.all(np.isfinite(imag_values)),
+            "Imaginary component should have valid values",
+        )
+
+    def test_large_raster_performance(self):
+        """Assess performance with a larger raster."""
+        self.runModule("g.region", n=90, s=-90, e=180, w=-180, rows=1000, cols=1000)
+        self.runModule(
+            "r.mapcalc", expression=f"{self.input_raster} = col()", overwrite=True
+        )
+
+        self.assertModule(
+            "i.fft",
+            input=self.input_raster,
+            real=self.real_output,
+            imaginary=self.imag_output,
+            overwrite=True,
+        )
+
+        self.assertRasterExists(self.real_output)
+        self.assertRasterExists(self.imag_output)
+
+
+if __name__ == "__main__":
+    test()