diff --git a/myscan/app.py b/myscan/app.py
index fe4f1b5..4af5574 100644
--- a/myscan/app.py
+++ b/myscan/app.py
@@ -30,22 +30,30 @@ from .ocr import Ocr, layout, paragraph_joins, reflow, text_direction
 IMAGE_FILTER = "Images (*.png *.jpg *.jpeg *.tif *.tiff *.bmp *.webp)"
 
 
-def to_qimage(img, page=False):
-    """BGR or grayscale uint8 array -> QImage (a copy). With `page`, exact-white pixels
-    (the uncovered corners of a stitched page) become transparent, so when the view
-    rotates the page to level it those corners show the window background through."""
+def to_qimage(img, transparent=None):
+    """BGR or grayscale uint8 array -> QImage (a copy); pixels where the bool mask
+    `transparent` is set get alpha 0."""
     img = np.ascontiguousarray(img)
     h, w = img.shape[:2]
-    if not page:
+    if transparent is None:
         fmt = QImage.Format_Grayscale8 if img.ndim == 2 else QImage.Format_BGR888
         return QImage(img.data, w, h, img.strides[0], fmt).copy()
     bgra = cv2.cvtColor(img, cv2.COLOR_GRAY2BGRA if img.ndim == 2 else cv2.COLOR_BGR2BGRA)
-    uncovered = (img == 255).all(axis=-1) if img.ndim == 3 else (img == 255)
-    bgra[uncovered, 3] = 0
-    bgra = np.ascontiguousarray(bgra)
+    bgra[transparent, 3] = 0
     return QImage(bgra.data, w, h, bgra.strides[0], QImage.Format_ARGB32).copy()
 
 
+def unscanned(img):
+    """Mask of a stitched page's unscanned area: the pure-white regions touching the
+    border (the stitcher fills uncovered pixels with 255 and crops to the scanned area).
+    Paper that clips to 255 inside the page is not connected to the border and stays."""
+    white = ((img == 255).all(axis=-1) if img.ndim == 3 else img == 255).astype(np.uint8)
+    _, labels = cv2.connectedComponents(white, connectivity=4)
+    edge = np.concatenate([labels[0], labels[-1], labels[:, 0], labels[:, -1]])
+    edge = np.unique(edge[edge > 0])
+    return np.isin(labels, edge) if len(edge) else None
+
+
 def imread(path):
     """cv2.imread that also takes non-ASCII paths on Windows."""
     return cv2.imdecode(np.fromfile(path, np.uint8), cv2.IMREAD_COLOR)
@@ -98,7 +106,7 @@ class Bridge(QObject):
         self.start_event, self.stop_event = threading.Event(), threading.Event()
 
     def publish(self, name, bgr):
-        (self.frame if name == "frame" else self.page).emit(to_qimage(bgr, page=(name == "page")))
+        (self.frame if name == "frame" else self.page).emit(to_qimage(bgr))
 
     def set_status(self, **kw):
         self.state = {**self.state, **kw}
@@ -567,6 +575,7 @@ class MainWindow(QMainWindow):
         self.opts = opts
         self.ocr = Ocr()
         self.image, self.path, self.lines, self.text = None, None, [], ""
+        self.blank = None           # unscanned-area mask of the shown page (set_page)
         self.page_title = "Page"
         self.ocr_thread, self.scan_thread, self.scanning = None, None, False
         self.page_id = 0            # bumped for every new page, so a slow OCR of an old one is not applied
@@ -720,11 +729,11 @@ class MainWindow(QMainWindow):
 
     def on_result(self, path):
         self.scanning = False
-        self.load(path)
+        self.load(path, scanned=True)
 
     # ---- images ----
 
-    def load(self, path):
+    def load(self, path, scanned=False):
         try:
             img = imread(path)
         except OSError:
@@ -733,15 +742,18 @@ class MainWindow(QMainWindow):
             log_error(f"cannot read {path}")
             QMessageBox.warning(self, "myScan", f"cannot read {path}")
             return
-        self.set_page(img, path)
+        self.set_page(img, path, scanned)
         self.run_ocr()
 
-    def set_page(self, img, path=None):
+    def set_page(self, img, path=None, scanned=False):
+        """`scanned`: a fresh stitched page, whose unscanned corners are shown transparent
+        (opened images are shown as they are: their white may be paper)."""
         self.image, self.path, self.lines, self.text = img, path, [], ""
+        self.blank = unscanned(img) if scanned else None
         self.page_id += 1
         self.view.set_lines([])
         self.view.angle = 0.0
-        self.view.set_image(to_qimage(img, page=True))
+        self.view.set_image(to_qimage(img, self.blank))
         name = os.path.basename(path) if path else "page"
         self.page_title = f"Page — {name}  ({img.shape[1]}×{img.shape[0]})"
         self.page_head.setText(self.page_title)
@@ -808,7 +820,9 @@ class MainWindow(QMainWindow):
             return
         if flipped:          # the boxes are on the page turned the right way up
             self.image = np.ascontiguousarray(self.image[::-1, ::-1])
-            self.view.set_image(to_qimage(self.image, page=True))
+            if self.blank is not None:
+                self.blank = self.blank[::-1, ::-1]
+            self.view.set_image(to_qimage(self.image, self.blank))
         self.lines = lines
         self.text, spans = layout(lines)
         self.view.set_lines(lines, self.text, spans)