Live button-driven scanning with EEPROM calibration

- ScanSession: scan-mode context manager with bright-pixel auto-exposure and
  sensor colour gains; tools/scan.py scans on the scan button with live stitching
- Read-only EEPROM access and calib.py parser (laser geometry, intrinsics,
  colour gains, black/white flat-field samples); flat-field correction in Stitcher
- OV7740 sensor access via the MCU proxy; colour gains from EEPROM fix green cast
- Stitcher: colour support, high-passed registration (robust on blank paper)
- RE notes on the Mac app's colour, exposure, stitching and button handling

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/stitch.py

@@ -10,7 +10,8 @@ sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
 import cv2  # noqa: E402
 import numpy as np  # noqa: E402
 
-from myscan.stitch import ROT_GAIN, Stitcher, laser_deltas  # noqa: E402
+from myscan import calib  # noqa: E402
+from myscan.stitch import ROT_GAIN, Stitcher  # noqa: E402
 
 
 def main():
@@ -19,24 +20,26 @@ def main():
     ap.add_argument("-o", "--out", help="output image (default <dir>/page.png)")
     ap.add_argument("--no-refine", action="store_true", help="lasers only, no image registration")
     ap.add_argument("--rot-gain", type=float, default=ROT_GAIN)
+    ap.add_argument("--no-flat", action="store_true", help="skip the EEPROM flat-field correction")
+    ap.add_argument("--no-wb", action="store_true", help="skip white-patch balancing")
     ap.add_argument("--start", type=int, default=0)
     ap.add_argument("--end", type=int)
     a = ap.parse_args()
 
     rows = list(csv.DictReader(open(os.path.join(a.dir, "records.csv"))))
     v = np.array([[int(r[f"v{k}"]) for k in range(6)] for r in rows])
-    deltas = laser_deltas(v)
     frames = [int(r["frame"]) for r in rows]
     rng = range(a.start, a.end if a.end is not None else len(rows))
 
+    flat = None if a.no_flat else calib.FlatField(calib.load())
     st = None
     for i in rng:
-        im = cv2.imread(os.path.join(a.dir, f"f{frames[i]:05d}.png"), cv2.IMREAD_GRAYSCALE)
+        im = cv2.imread(os.path.join(a.dir, f"f{frames[i]:05d}.png"), cv2.IMREAD_UNCHANGED)
         if st is None:
-            st = Stitcher(im.shape, refine=not a.no_refine, rot_gain=a.rot_gain)
-        st.add(im, deltas[i])
+            st = Stitcher(im.shape, refine=not a.no_refine, rot_gain=a.rot_gain, flat=flat)
+        st.add(im, v[i])
     out = a.out or os.path.join(a.dir, "page.png")
-    cv2.imwrite(out, st.image())
+    cv2.imwrite(out, st.image(white_balance=not a.no_wb))
     print(f"{st.n} frames -> {out}  {st.stats}")