Split stitching into a hardware-independent myscan.stitching package

stitch.py and pagegraph.py mixed laser odometry, image registration,
frame correction, canvas handling, pose-graph maths and the two stitchers.
They are now modules of myscan/stitching, which imports nothing from the
device code:

  geometry    rigid transforms, pose vectors, warp_add
  filters     grayscale, high-pass, feather weights
  correct     Corrector: undistortion + flat field (and weighted variant)
  odometry    LaserOdometry: the laser model and the phase-correlation
              override, shared by both stitchers
  register    ECC, phase correlation, SIFT matching, overlap agreement
  canvas      growable Canvas, layout, parallel render, normalize/compose
  posegraph   robust Gauss-Newton, largest connected component
  loops       keyframes and loop-closure candidates
  pagegraph   PageGraph, now orchestration only
  incremental Stitcher, on the shared Canvas

The stitchers take a Corrector and an odometry object (anything with
predict()) instead of building them, so another device can supply its
own motion prior. live.py drops its own canvas and normalisation for the
shared ones; PageGraph's mosaic check uses the parallel renderer.

Output on scan_text is unchanged (global stitcher identical, incremental
within 1 grey level). stitch.py --live now applies lens correction too
(--no-undistort restores the old output).

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

tools/stitch.py

@@ -11,15 +11,14 @@ import cv2  # noqa: E402
 import numpy as np  # noqa: E402
 
 from myscan import calib  # noqa: E402
-from myscan.pagegraph import PageGraph  # noqa: E402
-from myscan.stitch import ROT_GAIN, Stitcher  # noqa: E402
+from myscan.stitching import ROT_GAIN, Corrector, LaserOdometry, PageGraph, Stitcher  # noqa: E402
 
 
 def main():
     ap = argparse.ArgumentParser()
     ap.add_argument("dir")
     ap.add_argument("-o", "--out", help="output image (default <dir>/page.png)")
-    ap.add_argument("--live", action="store_true", help="use the live frame-by-frame stitcher instead of the global one")
+    ap.add_argument("--live", action="store_true", help="use the incremental frame-by-frame stitcher")
     ap.add_argument("--no-refine", action="store_true", help="with --live: 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")
@@ -35,14 +34,14 @@ def main():
     rng = range(a.start, a.end if a.end is not None else len(rows))
 
     cal = calib.load()
-    flat = None if a.no_flat else calib.FlatField(cal)
-    undistort = None if a.no_undistort else calib.Undistort(cal)
+    corrector = Corrector(None if a.no_flat else calib.FlatField(cal),
+                          None if a.no_undistort else calib.Undistort(cal))
     st = None
     for i in rng:
         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, flat=flat) if a.live
-                  else PageGraph(im.shape, flat=flat, undistort=undistort, rot_gain=a.rot_gain))
+            st = (Stitcher(im.shape, corrector, LaserOdometry(a.rot_gain, max_step_rot=None), refine=not a.no_refine)
+                  if a.live else PageGraph(im.shape, corrector, LaserOdometry(a.rot_gain)))
         st.add(im, v[i])
     out = a.out or os.path.join(a.dir, "page.png")
     cv2.imwrite(out, st.image(white_balance=not a.no_wb))