Add Export Fused ROI CSV export

Lets a user export the current ROI as one CSV with a column per selected
angle's value (RF peak freq, Bias A, Bias B, or velocity), once angles share
a common (x, y) grid -- either via a live Fusion alignment result or because
the open file is itself a previous Alignment Wizard export whose angles
already share one grid on disk. Never triggers a background compute; angles
without cached/stored data for the chosen value type are simply unavailable
in the picker.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

sras_format.py

@@ -770,6 +770,24 @@ class SrasFile:
     def y_positions_mm(self, angle_idx: int) -> np.ndarray:
         return self._y_pos_per_angle[angle_idx]
 
+    def angles_share_raw_grid(self) -> bool:
+        """True iff every angle's raw (x, y) pixel grid is literally the same
+        array as angle 0's -- the case for a .sras file the viewer's own
+        Alignment Wizard exported (see scan_format.md, "Files written by the
+        viewer's Alignment Wizard"): the writer packs one Per-Angle Geometry
+        record and one Row Table span and repeats those same bytes for every
+        angle, so re-parsed arrays are bit-identical copies rather than
+        independently re-derived numbers -- a bare np.array_equal is the
+        correct test here, no tolerance needed.
+        """
+        if self.n_angles <= 1:
+            return True
+        x0 = self.x_axis_mm(0)
+        y0 = self.y_positions_mm(0)
+        return all(np.array_equal(self.x_axis_mm(a), x0)
+                   and np.array_equal(self.y_positions_mm(a), y0)
+                   for a in range(1, self.n_angles))
+
     def time_axis_ns(self) -> np.ndarray:
         return np.arange(self.samples_per_frame) / self.sample_rate_hz * 1e9
 

sras_viewer/__init__.py

@@ -23,5 +23,7 @@ from .canvases import (                                               # noqa: E4
     AlignOverlayCanvas, ImageCanvas, RoiQuad, WaveformCanvas,
 )
 from .common import CH_LABELS, CMAPS, VELOCITY_MODE_IDX              # noqa: E402,F401
-from .dialogs import FftOptionsDialog, RowAverageFftOptionsDialog    # noqa: E402,F401
+from .dialogs import (                                                # noqa: E402,F401
+    FftOptionsDialog, FusedRoiExportDialog, RowAverageFftOptionsDialog,
+)
 from .main_window import SrasViewerWindow, main                      # noqa: E402,F401

sras_viewer/dialogs.py

@@ -5,14 +5,18 @@ alignment wizard's first page (see align_wizard.py), which needed the same
 mask-overlay editor plus the crop and export steps.
 """
 
+from pathlib import Path
+
 from PyQt6.QtWidgets import (
-    QButtonGroup, QDialog, QDialogButtonBox, QGroupBox, QHBoxLayout, QLabel,
-    QRadioButton, QSpinBox, QVBoxLayout,
+    QButtonGroup, QCheckBox, QDialog, QDialogButtonBox, QFileDialog,
+    QGroupBox, QHBoxLayout, QLabel, QLineEdit, QPushButton, QRadioButton,
+    QScrollArea, QSpinBox, QVBoxLayout, QWidget,
 )
 
 from sras_compute import PYFFTW_AVAILABLE
+from sras_format import CH1_IDX, CH3_IDX, CH4_IDX, CH_NAMES
 
-from .common import _CSS_HINT, _make_dspin
+from .common import CH_LABELS, VELOCITY_MODE_IDX, _CSS_HINT, _CSS_WARN, _group, _make_dspin, _wrap_label
 
 
 # ---------------------------------------------------------------------------
@@ -235,3 +239,177 @@ class RowAverageFftOptionsDialog(QDialog):
     def get_threshold_mv(self) -> float:
         return self._spin_threshold.value()
 
+
+# ---------------------------------------------------------------------------
+# Export Fused ROI dialog
+# ---------------------------------------------------------------------------
+
+class FusedRoiExportDialog(QDialog):
+    """Choose a value type and which angles to fuse for Export Fused ROI.
+
+    Every angle in the file is listed (a live AlignmentResult's per_angle
+    always covers every angle, and the raw-shared-grid path needs no per-
+    angle transform at all). Each checkbox is disabled — and auto-unchecked
+    — whenever *availability_fn(angle_idx, ch_idx)* is False for the
+    currently selected value type; switching the value-type radio
+    re-evaluates every checkbox live, since availability is per (angle,
+    value type) rather than just per angle — e.g. DC may be ready
+    everywhere while FFT is ready nowhere.
+    """
+
+    _VALUE_MODES = (CH1_IDX, CH3_IDX, CH4_IDX, VELOCITY_MODE_IDX)
+
+    def __init__(self, parent=None, *,
+                 angles: list[tuple[int, float]],
+                 availability_fn,
+                 default_ch_idx: int,
+                 out_dir: str,
+                 stem: str,
+                 grid_note: str):
+        super().__init__(parent)
+        self.setWindowTitle("Export Fused ROI")
+        self.setModal(True)
+        self.setMinimumWidth(420)
+
+        self._availability_fn = availability_fn
+        self._out_dir = out_dir
+        self._stem = stem
+        self._path_user_chosen = False
+
+        layout = QVBoxLayout(self)
+        layout.addWidget(_wrap_label(grid_note, _CSS_HINT))
+
+        # ---- Value type --------------------------------------------------
+        grp_val, vl = _group("Value to Export")
+        self._val_group = QButtonGroup(self)
+        self._val_buttons: dict[int, QRadioButton] = {}
+        for ch_idx, label in zip(self._VALUE_MODES, CH_LABELS):
+            rb = QRadioButton(label)
+            self._val_group.addButton(rb, id=ch_idx)
+            self._val_buttons[ch_idx] = rb
+            vl.addWidget(rb)
+        self._val_buttons[default_ch_idx].setChecked(True)
+        self._val_group.idClicked.connect(self._on_value_type_changed)
+        layout.addWidget(grp_val)
+
+        # ---- Angles --------------------------------------------------
+        grp_ang, al = _group("Angles to Include")
+        sel_row = QHBoxLayout()
+        btn_all = QPushButton("Select All Available")
+        btn_none = QPushButton("Select None")
+        btn_all.clicked.connect(self._on_select_all_available)
+        btn_none.clicked.connect(self._on_select_none)
+        sel_row.addWidget(btn_all)
+        sel_row.addWidget(btn_none)
+        al.addLayout(sel_row)
+
+        scroll_inner = QWidget()
+        scroll_layout = QVBoxLayout(scroll_inner)
+        self._angle_checks: dict[int, QCheckBox] = {}
+        for angle_idx, angle_deg in angles:
+            cb = QCheckBox(f"{angle_deg:.1f}°  (angle {angle_idx})")
+            self._angle_checks[angle_idx] = cb
+            cb.toggled.connect(self._update_accept_enabled)
+            scroll_layout.addWidget(cb)
+        scroll = QScrollArea()
+        scroll.setWidget(scroll_inner)
+        scroll.setWidgetResizable(True)
+        scroll.setMaximumHeight(220)
+        al.addWidget(scroll)
+
+        self._lbl_none_available = _wrap_label("", _CSS_WARN)
+        al.addWidget(self._lbl_none_available)
+        layout.addWidget(grp_ang)
+
+        # ---- Output path --------------------------------------------------
+        grp_out, ol = _group("Output File")
+        path_row = QHBoxLayout()
+        self._edit_path = QLineEdit()
+        self._edit_path.setReadOnly(True)
+        path_row.addWidget(self._edit_path, 1)
+        btn_browse = QPushButton("Browse…")
+        btn_browse.clicked.connect(self._on_browse)
+        path_row.addWidget(btn_browse)
+        ol.addLayout(path_row)
+        layout.addWidget(grp_out)
+
+        # ---- Buttons -----------------------------------------------------
+        buttons = QDialogButtonBox()
+        self._btn_export = buttons.addButton(
+            "Export", QDialogButtonBox.ButtonRole.AcceptRole)
+        self._btn_export.clicked.connect(self.accept)
+        buttons.addButton("Cancel", QDialogButtonBox.ButtonRole.RejectRole
+                          ).clicked.connect(self.reject)
+        layout.addWidget(buttons)
+
+        self._refresh_default_path()
+        self._apply_availability()
+
+    # ---- internals -----------------------------------------------------
+
+    def _current_ch_idx(self) -> int:
+        return self._val_group.checkedId()
+
+    def _apply_availability(self):
+        ch_idx = self._current_ch_idx()
+        n_ok = 0
+        for angle_idx, cb in self._angle_checks.items():
+            ok = self._availability_fn(angle_idx, ch_idx)
+            cb.setEnabled(ok)
+            if ok:
+                n_ok += 1
+                cb.setToolTip("")
+            else:
+                cb.setChecked(False)
+                cb.setToolTip(
+                    f"No cached/stored {CH_LABELS[ch_idx]} data for this "
+                    "angle yet — view it in the main window (or run "
+                    "Batch Compute) first.")
+        self._lbl_none_available.setText(
+            "" if n_ok else "No angle has this value type ready yet.")
+        self._update_accept_enabled()
+
+    def _on_value_type_changed(self, _id: int):
+        self._apply_availability()
+        if not self._path_user_chosen:
+            self._refresh_default_path()
+
+    def _on_select_all_available(self):
+        for cb in self._angle_checks.values():
+            if cb.isEnabled():
+                cb.setChecked(True)
+
+    def _on_select_none(self):
+        for cb in self._angle_checks.values():
+            cb.setChecked(False)
+
+    def _refresh_default_path(self):
+        ch_idx = self._current_ch_idx()
+        name = f"{self._stem}_fused_roi_{CH_NAMES[ch_idx]}.csv"
+        self._edit_path.setText(str(Path(self._out_dir) / name))
+        self._update_accept_enabled()
+
+    def _on_browse(self):
+        path, _ = QFileDialog.getSaveFileName(
+            self, "Export Fused ROI as CSV", self._edit_path.text(),
+            "CSV files (*.csv);;All files (*)")
+        if path:
+            self._edit_path.setText(path)
+            self._path_user_chosen = True
+            self._update_accept_enabled()
+
+    def _update_accept_enabled(self):
+        any_checked = any(cb.isChecked() for cb in self._angle_checks.values())
+        self._btn_export.setEnabled(any_checked and bool(self._edit_path.text()))
+
+    # ---- getters ---------------------------------------------------------
+
+    def get_ch_idx(self) -> int:
+        return self._current_ch_idx()
+
+    def get_selected_angles(self) -> list[int]:
+        return sorted(a for a, cb in self._angle_checks.items() if cb.isChecked())
+
+    def get_output_path(self) -> str:
+        return self._edit_path.text()
+

sras_viewer/main_window.py

@@ -34,7 +34,9 @@ from .common import (
     _wrap_label,
 )
 from .align_wizard import AlignmentWizard
-from .dialogs import FftOptionsDialog, RowAverageFftOptionsDialog
+from .dialogs import (
+    FftOptionsDialog, FusedRoiExportDialog, RowAverageFftOptionsDialog,
+)
 
 # ---------------------------------------------------------------------------
 # Main window
@@ -335,6 +337,11 @@ class SrasViewerWindow(QMainWindow):
         self.btn_export_roi.clicked.connect(self._on_export_roi_csv)
         rl.addWidget(self.btn_export_roi)
 
+        self.btn_export_fused_roi = QPushButton("Export Fused ROI…")
+        self.btn_export_fused_roi.setEnabled(False)
+        self.btn_export_fused_roi.clicked.connect(self._on_export_fused_roi_csv)
+        rl.addWidget(self.btn_export_fused_roi)
+
         self.lbl_roi_center = _wrap_label("centroid: —", _CSS_HINT)
         self.lbl_roi_size = _wrap_label("bbox: —", _CSS_HINT)
         self.lbl_roi_npix = _wrap_label("pixels inside: —", _CSS_HINT)
@@ -826,6 +833,91 @@ class SrasViewerWindow(QMainWindow):
         self.statusBar().showMessage(
             f"Exported ROI ({n_pix} pixels) to {Path(path).name}")
 
+    def _on_export_fused_roi_csv(self):
+        s = self._sras
+        if s is None:
+            return
+        roi = self.image_canvas.get_roi()
+        if roi is None or not self._fused_grid_ready():
+            return   # button is disabled in these states; defensive no-op
+
+        angles = [(a, float(s.angles_deg[a])) for a in range(s.n_angles)]
+        grid_note = (
+            "Using the live Fusion alignment canvas."
+            if self._alignment_result is not None else
+            "Using the file's shared raw grid (no live alignment result — "
+            "this file's angles already share one grid).")
+        dlg = FusedRoiExportDialog(
+            self, angles=angles,
+            availability_fn=lambda a, c: self._cached_value_image(a, c) is not None,
+            default_ch_idx=self.combo_channel.currentIndex(),
+            out_dir=str(s.path.parent), stem=s.path.stem, grid_note=grid_note)
+        if dlg.exec() != QDialog.DialogCode.Accepted:
+            return
+        self._write_fused_roi_csv(
+            roi, dlg.get_ch_idx(), dlg.get_selected_angles(), dlg.get_output_path())
+
+    def _write_fused_roi_csv(self, roi, ch_idx: int, angle_idxs: list[int],
+                             out_path: str):
+        """Mask once on the fused grid, then one value column per selected
+        angle. No row/frame index columns: once angles are fused onto one
+        shared canvas there is no single meaningful raw (row, frame) per
+        output pixel, unlike the single-angle _on_export_roi_csv above."""
+        s = self._sras
+        if s is None or not angle_idxs or not out_path:
+            return
+        x_axis, y_axis = self._fused_export_axes()
+        mask = roi.mask_for_grid(x_axis, y_axis)
+        if not mask.any():
+            self.statusBar().showMessage(
+                "ROI does not overlap any pixel on the fused grid")
+            return
+
+        columns: list[np.ndarray] = []
+        used: list[int] = []
+        skipped: list[int] = []
+        for a in angle_idxs:
+            img = self._fused_value_image(a, ch_idx)
+            if img is None or img.shape != mask.shape:
+                # Defensive only: nothing else can mutate the caches between
+                # dialog-accept and this synchronous call in a single-
+                # threaded GUI callback, so this should never trigger — skip
+                # the angle rather than abort the whole export.
+                skipped.append(a)
+                continue
+            columns.append(img[mask].astype(np.float64))
+            used.append(a)
+
+        if not columns:
+            self.statusBar().showMessage(
+                "Nothing to export — no selected angle had data")
+            return
+
+        X, Y = np.meshgrid(np.asarray(x_axis, dtype=np.float64),
+                           np.asarray(y_axis, dtype=np.float64))
+        data = np.column_stack([X[mask], Y[mask], *columns])
+
+        ch_name = CH_NAMES[ch_idx]
+        corners_str = "  ".join(f"({p[0]:.6g},{p[1]:.6g})" for p in roi.corners())
+        angle_list_str = ", ".join(f"{s.angles_deg[a]:.4g}°" for a in used)
+        header_cols = ["x_mm", "y_mm"] + [f"v_{s.angles_deg[a]:.4g}deg" for a in used]
+        header = (
+            f"# ROI quad corners (BL BR TR TL) mm: {corners_str}\n"
+            f"# source: {s.path.name}, value={ch_name}, "
+            f"grid={'aligned canvas' if self._alignment_result is not None else 'shared raw grid'}\n"
+            f"# angles (deg): {angle_list_str}\n"
+            f"# n_pixels={int(mask.sum())}\n"
+            + ",".join(header_cols)
+        )
+        np.savetxt(out_path, data, delimiter=",",
+                   fmt=["%.6g"] * data.shape[1], header=header, comments="")
+
+        note = (f" ({len(skipped)} angle(s) skipped — no longer available)"
+                if skipped else "")
+        self.statusBar().showMessage(
+            f"Exported fused ROI ({int(mask.sum())} pixels, {len(used)} "
+            f"angle(s)) to {Path(out_path).name}{note}")
+
     # ------------------------------------------------------------------
     # ROI
     # ------------------------------------------------------------------
@@ -855,6 +947,7 @@ class SrasViewerWindow(QMainWindow):
             self.lbl_roi_npix.setText("pixels inside: —")
             self.btn_clear_roi.setEnabled(False)
             self.btn_export_roi.setEnabled(False)
+            self._update_fused_export_enabled()
             return
 
         cen = roi.centroid()
@@ -878,6 +971,26 @@ class SrasViewerWindow(QMainWindow):
         self.lbl_roi_npix.setText(f"pixels inside: {npix}")
         self.btn_clear_roi.setEnabled(True)
         self.btn_export_roi.setEnabled(self._current_image is not None and npix > 0)
+        self._update_fused_export_enabled()
+
+    def _update_fused_export_enabled(self):
+        s = self._sras
+        roi = self.image_canvas.get_roi() if s is not None else None
+        if s is None:
+            ready, reason = False, "Open a file first."
+        elif roi is None:
+            ready, reason = False, "Draw an ROI first."
+        elif not self._fused_grid_ready():
+            ready, reason = False, (
+                "Angles need a common grid to fuse: run Fusion → Alignment "
+                "Wizard, or open a file the wizard already exported.")
+        else:
+            ready, reason = True, (
+                "Export the ROI as one CSV with a column per selected "
+                "angle's value (choose which value and which angles in "
+                "the dialog).")
+        self.btn_export_fused_roi.setEnabled(ready)
+        self.btn_export_fused_roi.setToolTip(reason)
 
     # ------------------------------------------------------------------
     # Display
@@ -934,6 +1047,46 @@ class SrasViewerWindow(QMainWindow):
             self._aligned_cache[key] = cached
         return cached
 
+    # ------------------------------------------------------------------
+    # Fused ROI export (Export Fused ROI…)
+    # ------------------------------------------------------------------
+
+    def _fused_grid_ready(self) -> bool:
+        """Is there a common (x, y) grid to fuse angles onto right now?
+
+        Either a live alignment result exists (angles are reconciled onto its
+        canvas via apply_alignment), or — with no alignment run this session
+        — the open file's raw per-angle grids already coincide, which is true
+        for a .sras file the Alignment Wizard itself previously exported (see
+        scan_format.md, "Files written by the viewer's Alignment Wizard")."""
+        return (self._sras is not None
+                and (self._alignment_result is not None
+                     or self._sras.angles_share_raw_grid()))
+
+    def _fused_export_axes(self) -> tuple[np.ndarray, np.ndarray]:
+        """(x_axis, y_axis) a fused ROI export masks and labels against: the
+        alignment canvas when a live result exists — the more current,
+        deliberate source of truth even if the raw grids happen to already
+        match too — else the grid every angle already shares."""
+        if self._alignment_result is not None:
+            return self._aligned_canvas_axes()
+        s = self._sras
+        return s.x_axis_mm(0), s.y_positions_mm(0)
+
+    def _fused_value_image(self, angle_idx: int, ch_idx: int) -> np.ndarray | None:
+        """One angle's image on the fused grid for (angle, channel), scaled
+        exactly like the on-screen display — so a Velocity export and the
+        on-screen Velocity image share the same scaling code. None if
+        nothing is cached/stored for this angle/channel without a compute."""
+        raw = self._cached_value_image(angle_idx, ch_idx)
+        if raw is None:
+            return None
+        img = (self._scale_for_display(raw, ch_idx)
+               if ch_idx in CH1_DERIVED_MODES else raw)
+        if self._alignment_result is not None:
+            return self._get_aligned_display_image(img, angle_idx, ch_idx)
+        return img   # angles already share the raw grid — no resample needed
+
     def _stored_fft_image(self, angle_idx: int) -> np.ndarray | None:
         """The open file's own stored peak-frequency image for this angle,
         masked and ready to display, or None if the file has nothing stored
@@ -967,6 +1120,42 @@ class SrasViewerWindow(QMainWindow):
             dc4_mv=self._dc_cache.get((angle_idx, CH4_IDX)),
             allow_dc_recompute=False)
 
+    def _cached_value_image(self, angle_idx: int, ch_idx: int) -> np.ndarray | None:
+        """The already-available (no compute) image for (angle, channel):
+        this window's own in-session dicts first, then the file's stored
+        v5/v7 cache blocks — the same two tiers, in the same cost order, that
+        _refresh_display and Export Fused ROI both need, so both share this
+        one lookup rather than drifting apart. None means genuinely nothing
+        is cached/stored, i.e. only a real compute could produce it — and
+        neither caller here is allowed to trigger one: _refresh_display falls
+        back to _start_compute() itself, and a fused export simply treats the
+        angle as unavailable.
+
+        For CH1/Velocity this is the unscaled, already-masked peak-frequency
+        (MHz) image; callers displaying/exporting Velocity must still run it
+        through _scale_for_display.
+        """
+        s = self._sras
+        if s is None:
+            return None
+        if ch_idx in CH1_DERIVED_MODES:
+            key = self._fft_cache_key(angle_idx)
+            raw = self._fft_cache.get(key)
+            if raw is None:
+                raw = self._stored_fft_image(angle_idx)
+                if raw is not None:
+                    # Masking the stored image is cheap but not free; keep the
+                    # result so revisiting this angle costs nothing at all.
+                    self._fft_cache[key] = raw
+            return raw
+        # A stored DC image needs no post-processing, so the file's own
+        # parsed array is served directly — as the compute path already
+        # does, _current_image is treated as read-only by every consumer.
+        cached = self._dc_cache.get((angle_idx, ch_idx))
+        if cached is None:
+            cached = s.cached_dc_mv(angle_idx, ch_idx)
+        return cached
+
     def _refresh_display(self):
         """Show the image for the current angle/channel/threshold, using
         cached data whenever possible and only falling back to a background
@@ -983,28 +1172,11 @@ class SrasViewerWindow(QMainWindow):
         angle_idx = self.spin_angle.value()
         ch_idx = self.combo_channel.currentIndex()
 
-        if ch_idx in CH1_DERIVED_MODES:
-            key = self._fft_cache_key(angle_idx)
-            raw = self._fft_cache.get(key)
-            if raw is None:
-                raw = self._stored_fft_image(angle_idx)
+        raw = self._cached_value_image(angle_idx, ch_idx)
         if raw is not None:
-                    # Masking the stored image is cheap but not free; keep the
-                    # result so revisiting this angle costs nothing at all.
-                    self._fft_cache[key] = raw
-            if raw is not None:
-                self._show_image_now(self._scale_for_display(raw, ch_idx),
-                                     angle_idx, ch_idx)
-                return
-        else:
-            # A stored DC image needs no post-processing, so the file's own
-            # parsed array is served directly — as the compute path already
-            # does, _current_image is treated as read-only by every consumer.
-            cached = self._dc_cache.get((angle_idx, ch_idx))
-            if cached is None:
-                cached = self._sras.cached_dc_mv(angle_idx, ch_idx)
-            if cached is not None:
-                self._show_image_now(cached, angle_idx, ch_idx)
+            img = (self._scale_for_display(raw, ch_idx)
+                   if ch_idx in CH1_DERIVED_MODES else raw)
+            self._show_image_now(img, angle_idx, ch_idx)
             return
 
         # Nothing cached for these settings — need a real compute. Changing

tests/test_fused_export.py

@@ -0,0 +1,75 @@
+"""SrasFile.angles_share_raw_grid(): the no-alignment-needed gating path for
+Export Fused ROI.
+
+A plain multi-angle scan gives each angle its own bounding box and stage
+x_start (scan_format.md's whole reason v6 geometry is per-angle), so it must
+read as "not shareable" without a live alignment. A file the viewer's own
+Alignment Wizard exported repeats one Per-Angle Geometry record and one Row
+Table span for every angle (scan_format.md, "Files written by the viewer's
+Alignment Wizard"), so it must read as "shareable" with no alignment needed
+at all.
+
+No Qt: this exercises sras_format/sras_compute/sras_align_export directly,
+mirroring tests/test_align_export.py.
+"""
+
+import sras_align_export as export
+import sras_compute as compute
+from sras_format import SrasFile
+import tools.make_test_sras as gen
+
+_THRESHOLD_MV = 80.0
+
+
+def test_single_angle_file_always_shares_its_grid(tmp_path):
+    path = tmp_path / "one_angle.sras"
+    gen.write(path, n_angles=1)
+    sras = SrasFile(str(path))
+    assert sras.angles_share_raw_grid()
+
+
+def test_plain_multi_angle_file_does_not_share_its_grid(tmp_path):
+    """tools.make_test_sras.write gives every angle its own geometry and
+    stage x_start (build()'s `x_start = -0.5 + 0.1 * a`), matching how real
+    v6 scans vary per angle — so this must read as "not shareable"."""
+    path = tmp_path / "plain.sras"
+    gen.write(path, n_angles=3)
+    sras = SrasFile(str(path))
+    assert not sras.angles_share_raw_grid()
+
+
+def test_wizard_exported_file_shares_its_grid(tmp_path):
+    src_path = tmp_path / "rotating.sras"
+    meta = gen.write_rotating(src_path, n_angles=4)
+    sras = SrasFile(str(src_path))
+    params = {a: compute.ManualAngleParams(rot, shift)
+              for a, (rot, shift) in meta["truth"].items()}
+    result = compute.build_manual_alignment(sras, 0, _THRESHOLD_MV, params)
+
+    out_path = tmp_path / "rotating_aligned.sras"
+    export.write_aligned_sras(sras, result, out_path)
+    out = SrasFile(str(out_path))
+
+    assert not sras.angles_share_raw_grid(), (
+        "sanity check: the *source* rotating scan must NOT already share a "
+        "grid, or this test would not actually exercise the wizard export")
+    assert out.angles_share_raw_grid()
+
+
+def test_mutated_angle_breaks_the_shared_grid(tmp_path):
+    """A loaded SrasFile's x_start_mm is a public per-angle array (as
+    tests/test_gui.py::test_alignment_geometry_is_stage_independent also
+    relies on) -- mutating one angle's start must be visible here too."""
+    src_path = tmp_path / "rotating.sras"
+    meta = gen.write_rotating(src_path, n_angles=3)
+    sras = SrasFile(str(src_path))
+    params = {a: compute.ManualAngleParams(rot, shift)
+              for a, (rot, shift) in meta["truth"].items()}
+    result = compute.build_manual_alignment(sras, 0, _THRESHOLD_MV, params)
+    out_path = tmp_path / "rotating_aligned.sras"
+    export.write_aligned_sras(sras, result, out_path)
+    out = SrasFile(str(out_path))
+    assert out.angles_share_raw_grid()
+
+    out.x_start_mm[1] += 1.0
+    assert not out.angles_share_raw_grid()

tests/test_gui.py

@@ -20,11 +20,13 @@ import numpy as np
 import pytest
 from PyQt6.QtCore import QEventLoop, Qt, QTimer
 from PyQt6.QtTest import QTest
-from PyQt6.QtWidgets import QApplication, QMessageBox
+from PyQt6.QtWidgets import QApplication, QDialog, QMessageBox
 
 import sras_compute as compute
 from sras_format import CH1_IDX, CH3_IDX, CH4_IDX, SrasFile
-from sras_viewer import RoiQuad, SrasViewerWindow, VELOCITY_MODE_IDX
+from sras_viewer import (
+    FusedRoiExportDialog, RoiQuad, SrasViewerWindow, VELOCITY_MODE_IDX,
+)
 import tools.make_test_sras as gen
 
 
@@ -670,6 +672,188 @@ def test_wizard_closes_with_a_reload(ctx):
     ctx.s = win._sras
 
 
+# ---------------------------------------------------------------------------
+# Export Fused ROI
+# ---------------------------------------------------------------------------
+#
+# Two independent ways angles can end up sharing one (x, y) grid to fuse
+# onto: a live alignment result (case a, exercised on ctx.win -- the reload
+# above restored one from the sidecar), or a file that is itself a previous
+# Alignment Wizard export, whose angles already share a grid on disk with no
+# alignment result needed at all (case b, exercised on a second window
+# opened on ctx.written from test_wizard_export).
+
+def test_fused_export_gating_case_a(ctx):
+    """A live alignment result bridges the raw scan's per-angle grids --
+    angles_share_raw_grid() alone would be False here."""
+    win, s = ctx.win, ctx.s
+    assert win._alignment_result is not None, "alignment restored from sidecar"
+    assert not s.angles_share_raw_grid(), \
+        "sanity check: the raw (un-aligned) scan must not already share a grid"
+
+    x, y = win._aligned_canvas_axes()
+    roi = RoiQuad.from_bbox(float(x[1]), float(y[1]), float(x[-2]), float(y[-2]))
+    win.image_canvas.set_roi(roi)
+    pump(120)
+    assert win._fused_grid_ready()
+    assert win.btn_export_fused_roi.isEnabled()
+
+
+def test_write_fused_roi_csv_case_a_content(ctx):
+    win, s = ctx.win, ctx.s
+    roi = win.image_canvas.get_roi()
+    assert roi is not None, "ROI drawn by test_fused_export_gating_case_a"
+
+    csv_path = ctx.tmpdir / "fused_roi_case_a.csv"
+    win._write_fused_roi_csv(roi, CH4_IDX, [0, 1], str(csv_path))
+    assert csv_path.exists()
+
+    lines = csv_path.read_text().splitlines()
+    body = [l for l in lines if not l.startswith("#")]
+    header, *data_lines = body
+    assert header == (
+        f"x_mm,y_mm,v_{s.angles_deg[0]:.4g}deg,v_{s.angles_deg[1]:.4g}deg")
+
+    x, y = win._fused_export_axes()
+    mask = roi.mask_for_grid(x, y)
+    assert len(data_lines) == int(mask.sum())
+
+    data = np.array([[float(v) for v in line.split(",")] for line in data_lines])
+    expect0 = win._fused_value_image(0, CH4_IDX)[mask]
+    expect1 = win._fused_value_image(1, CH4_IDX)[mask]
+    assert np.allclose(data[:, 2], expect0, rtol=1e-5, atol=1e-4)
+    assert np.allclose(data[:, 3], expect1, rtol=1e-5, atol=1e-4)
+
+
+def test_fused_roi_dialog_availability_live_updates(ctx):
+    """Switching the value-type radio re-evaluates every angle checkbox,
+    disabling/auto-unchecking whichever ones are no longer available --
+    independent of what actually backs availability_fn, so a synthetic
+    stand-in keeps this a fast, deterministic test of the dialog itself."""
+    win, s = ctx.win, ctx.s
+    angles = [(a, float(s.angles_deg[a])) for a in range(s.n_angles)]
+    only_angle0_has_ch1 = lambda a, c: (a == 0) if c == CH1_IDX else True
+
+    dlg = FusedRoiExportDialog(
+        win, angles=angles, availability_fn=only_angle0_has_ch1,
+        default_ch_idx=CH1_IDX, out_dir=str(s.path.parent), stem=s.path.stem,
+        grid_note="test")
+    try:
+        assert dlg._angle_checks[0].isEnabled()
+        assert all(not dlg._angle_checks[a].isEnabled()
+                   for a in range(1, s.n_angles))
+
+        dlg._angle_checks[0].setChecked(True)
+        dlg._val_buttons[CH4_IDX].click()
+        assert all(dlg._angle_checks[a].isEnabled() for a in range(s.n_angles)), \
+            "CH4 is available for every angle"
+        assert dlg._angle_checks[0].isChecked(), \
+            "stays checked -- still available under CH4"
+
+        if s.n_angles > 1:
+            dlg._angle_checks[1].setChecked(True)
+        dlg._val_buttons[CH1_IDX].click()
+        assert dlg._angle_checks[0].isChecked()
+        if s.n_angles > 1:
+            assert not dlg._angle_checks[1].isEnabled()
+            assert not dlg._angle_checks[1].isChecked(), \
+                "auto-unchecked: angle 1 has no data under CH1"
+    finally:
+        dlg.close()
+
+
+def test_fused_roi_dialog_select_all_none(ctx):
+    win, s = ctx.win, ctx.s
+    angles = [(a, float(s.angles_deg[a])) for a in range(s.n_angles)]
+    dlg = FusedRoiExportDialog(
+        win, angles=angles, availability_fn=lambda a, c: c == CH4_IDX,
+        default_ch_idx=CH4_IDX, out_dir=str(s.path.parent), stem=s.path.stem,
+        grid_note="test")
+    try:
+        assert not dlg._btn_export.isEnabled(), "nothing checked yet"
+        dlg._on_select_all_available()
+        assert all(cb.isChecked() for cb in dlg._angle_checks.values())
+        assert dlg._btn_export.isEnabled()
+        dlg._on_select_none()
+        assert not any(cb.isChecked() for cb in dlg._angle_checks.values())
+        assert not dlg._btn_export.isEnabled()
+    finally:
+        dlg.close()
+
+
+def test_on_export_fused_roi_csv_end_to_end(ctx):
+    win, s = ctx.win, ctx.s
+    roi = win.image_canvas.get_roi()
+    assert roi is not None, "ROI from the earlier fused-export tests is still set"
+
+    csv_path = ctx.tmpdir / "fused_roi_e2e.csv"
+    with patch("sras_viewer.main_window.FusedRoiExportDialog") as MockDlg:
+        inst = MockDlg.return_value
+        inst.exec.return_value = QDialog.DialogCode.Accepted
+        inst.get_ch_idx.return_value = CH4_IDX
+        inst.get_selected_angles.return_value = [0, 1]
+        inst.get_output_path.return_value = str(csv_path)
+        win.btn_export_fused_roi.click()
+
+    assert csv_path.exists()
+    kwargs = MockDlg.call_args.kwargs
+    assert kwargs["default_ch_idx"] == win.combo_channel.currentIndex()
+    assert kwargs["out_dir"] == str(s.path.parent)
+    assert kwargs["stem"] == s.path.stem
+
+
+def test_fused_export_no_alignment_shared_grid_path(ctx):
+    """ctx.written (from test_wizard_export) is itself a previous Alignment
+    Wizard export: opened fresh with no sidecar for its own path, so no
+    alignment result is ever restored -- but its angles already share one
+    grid on disk, so the export must work through the no-resample path."""
+    win2 = SrasViewerWindow()
+    try:
+        win2._load_file(str(ctx.written.path))
+        assert wait_until(lambda: win2._sras is not None)
+        s2 = win2._sras
+        assert win2._alignment_result is None, \
+            "no sidecar exists for this path -- nothing auto-restored"
+        assert s2.angles_share_raw_grid(), \
+            "a wizard export already shares one grid across angles"
+        assert wait_until(lambda: all((a, CH4_IDX) in win2._dc_cache
+                                      for a in range(s2.n_angles))), \
+            "DC precomputed for every angle"
+
+        x, y = s2.x_axis_mm(0), s2.y_positions_mm(0)
+        roi = RoiQuad.from_bbox(float(x[1]), float(y[1]), float(x[-2]), float(y[-2]))
+        win2.image_canvas.set_roi(roi)
+        pump(120)
+        assert win2._fused_grid_ready()
+        assert win2.btn_export_fused_roi.isEnabled()
+
+        aligned_cache_before = len(win2._aligned_cache)
+        angle_idxs = list(range(min(2, s2.n_angles)))
+        csv_path = ctx.tmpdir / "fused_roi_case_b.csv"
+        win2._write_fused_roi_csv(roi, CH4_IDX, angle_idxs, str(csv_path))
+        assert csv_path.exists()
+        assert len(win2._aligned_cache) == aligned_cache_before, \
+            "no-resample path must never touch apply_alignment"
+
+        header = next(l for l in csv_path.read_text().splitlines()
+                     if not l.startswith("#"))
+        expected_header = "x_mm,y_mm," + ",".join(
+            f"v_{s2.angles_deg[a]:.4g}deg" for a in angle_idxs)
+        assert header == expected_header
+
+        # Break the shared grid and confirm gating flips off.
+        mutate_idx = 1 if s2.n_angles > 1 else 0
+        s2.x_start_mm[mutate_idx] += 1.0
+        assert not s2.angles_share_raw_grid()
+        win2._update_fused_export_enabled()
+        assert not win2._fused_grid_ready()
+        assert not win2.btn_export_fused_roi.isEnabled()
+        assert "Alignment Wizard" in win2.btn_export_fused_roi.toolTip()
+    finally:
+        win2.close()
+        pump(200)
+
+
 def test_pixel_inspector(ctx):
     win = ctx.win
     win.chk_aligned_view.setChecked(False)