modest improvement to cropping (safer)

tests/test_ink_detection.py

@@ -108,6 +108,14 @@ class InkDetectionTests(unittest.TestCase):
                     .7,(190,190,190),2)
         self.assertGreater(detect_bounds(image,dpi=150)['bottom_px'],1100)
 
+    def test_sparse_central_pencil_on_dark_grid_survives(self):
+        image = self.dark_grid()
+        # Thin, pale handwriting crossing the ruling is split into sparse
+        # components. Its central position distinguishes it from page holes.
+        cv2.putText(image,'result',(330,1090),cv2.FONT_HERSHEY_SCRIPT_SIMPLEX,
+                    .85,(155,155,155),1)
+        self.assertGreater(detect_bounds(image,dpi=150)['bottom_px'],1090)
+
     def test_large_unruled_diagram_is_not_paper(self):
         image = np.full((1200,850,3),255,np.uint8)
         cv2.rectangle(image,(100,100),(750,1100),(20,20,20),3)
@@ -151,6 +159,12 @@ class InkDetectionTests(unittest.TestCase):
                 r = detect_bounds(image,dpi=150)
                 self.assertGreater(r['bottom_px'],1060)
 
+    def test_faint_page_number_in_outer_band_does_not_block_crop(self):
+        image = self.dark_grid()
+        cv2.putText(image,'4/',(3,1160),cv2.FONT_HERSHEY_SIMPLEX,
+                    .55,(130,130,130),1)
+        self.assertLess(detect_bounds(image,dpi=150)['bottom_px'],850)
+
     def test_faded_neutral_grid(self):
         image = self.dark_grid()
         image[np.all(image == 65,axis=2)] = 145