#
# Extract the OUT-OF-RANGE pixel mask from the positive-control capture.
#
# With BT_TRANS_PROVOKE the sec port's translationTable[64..255] is 0xFF00,
# so every pixel whose source index exceeded the 6-bit palette sets ALL the
# high-byte head bits.  Eng1 (0x0200) is sparse, so "Eng1 lit in provoke but
# not in shipped" isolates the offenders exactly.
#
import sys
from PIL import Image

BOX = (8, 52, 648, 531)
ENG1 = 0x0200


def words(path):
    im = Image.open(path).convert("RGB").crop(BOX)
    w, h = im.size
    px = im.load()
    return [[((px[x, y][0] >> 3) << 11) | ((px[x, y][1] >> 2) << 5) |
             (px[x, y][2] >> 3) for x in range(w)] for y in range(h)], w, h


A, w, h = words(sys.argv[1])   # shipped
B, _, _ = words(sys.argv[2])   # provoke

out = Image.new("RGB", (w, h), (0, 0, 0))
op = out.load()
runs = {}
n = 0
for y in range(h):
    run = 0
    for x in range(w):
        if (B[y][x] & ENG1) and not (A[y][x] & ENG1):
            op[x, y] = (255, 40, 0)
            n += 1
            run += 1
        else:
            if run:
                runs[run] = runs.get(run, 0) + 1
            run = 0
    if run:
        runs[run] = runs.get(run, 0) + 1

out.save(sys.argv[3])
print("out-of-range pixels: %d" % n)
print("horizontal run lengths (len: count), longest first:")
for k in sorted(runs, reverse=True)[:12]:
    print("   %3d px run  x%d" % (k, runs[k]))