Merge branch 'fix_halftomo_backproj' into 'master'

Fix halftomo plain backprojection when using numpy array

Closes #570

See merge request tomotools/nabu!543

nabu/reconstruction/fbp_base.py

@@ -354,7 +354,7 @@ class BackprojectorBase:
 
     def backproj(self, sino, output=None, do_checks=True):
         if self.halftomo and self.rot_center < self.dwidth:
-            self.sino_mult.prepare_sino(sino)
+            sino = self.sino_mult.prepare_sino(sino)
         self._transfer_to_texture(sino)
         d_slice = self._set_output(output, check=do_checks)
         self._set_kernel_slice_arg(d_slice)

nabu/reconstruction/tests/test_halftomo.py

@@ -99,6 +99,32 @@ class TestHalftomo:
         rot_center = sino.shape[-1] - 1 - self.rot_center
         return self.test_halftomo_right_side(config, sino=sino, rot_center=rot_center)
 
+    def test_halftomo_plain_backprojection(self, config):
+        backprojector = self._get_backprojector(
+            config,
+            self.sino.shape,
+            rot_center=self.rot_center,
+            halftomo=True,
+            padding_mode="edges",
+            extra_options={"centered_axis": True},
+        )
+        d_sino_filtered = backprojector.sino_filter.filter_sino(self.sino)  # device array
+        h_sino_filtered = d_sino_filtered.get()
+        reference_fbp = backprojector.fbp(self.sino)
+
+        def _check(rec, array_type):
+            assert (
+                np.max(np.abs(rec - reference_fbp)) < 1e-7
+            ), "Something wrong with halftomo backproj using %s array and configuration %s" % (array_type, str(config))
+
+        # Test with device array
+        rec_from_already_filtered_sino = backprojector.backproj(d_sino_filtered)
+        _check(rec_from_already_filtered_sino, "device")
+
+        # Test with numpy array
+        rec_from_already_filtered_sino = backprojector.backproj(h_sino_filtered)
+        _check(rec_from_already_filtered_sino, "numpy")
+
     def test_halftomo_cor_outside_fov(self, config):
         sino = np.ascontiguousarray(self.sino[:, : self.sino.shape[-1] // 2])
         backprojector = self._get_backprojector(config, sino.shape, rot_center=self.rot_center, halftomo=True)