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#!/usr/bin/env python3
"""Fail if the p40-night frame's Wu Peng boat is not dark enough against its glow.
The `LV_P40_SHOT=1` night hook centers tile (234,50) in a 1280x720 viewport; the
two-tile boat occupies tiles (234,50)-(235,50), so its screen box and the ring of
lantern glow around it are pure functions of those constants. The regression
budget is: mean luma of the boat box must be at least 40 grey below the mean luma
of a 24px ring around it.
Usage:
python3 scripts/check-p40-night-boat-contrast.py [p40-night.png]
Defaults to docs/evidence/p40-night.png. Exit 0 clean, 1 below budget, 2 on
usage/read error.
"""
import sys
from pathlib import Path
import numpy as np
from PIL import Image
MIN_CONTRAST = 40.0
TILE = 32
VIEW_W, VIEW_H = 1280, 720
BOAT_TX, BOAT_TY = 234, 50
RING = 24
def measure(path):
rgba = np.asarray(Image.open(path).convert("RGB"), dtype=np.float64)
luma = 0.299 * rgba[:, :, 0] + 0.587 * rgba[:, :, 1] + 0.114 * rgba[:, :, 2]
cam_x = BOAT_TX * TILE + TILE // 2 - VIEW_W // 2
cam_y = BOAT_TY * TILE + TILE // 2 - VIEW_H // 2
x0 = BOAT_TX * TILE - cam_x
y0 = BOAT_TY * TILE - cam_y
x1 = x0 + 2 * TILE
y1 = y0 + TILE
boat = float(luma[y0:y1, x0:x1].mean())
patch = luma[y0 - RING:y1 + RING, x0 - RING:x1 + RING].copy()
patch[RING:RING + TILE, RING:RING + 2 * TILE] = np.nan
ring = float(np.nanmean(patch))
return boat, ring
def main(argv):
target = Path(argv[1]) if len(argv) > 1 else Path("docs/evidence/p40-night.png")
if not target.is_file():
sys.stderr.write(f"missing frame: {target}\n")
return 2
boat, ring = measure(target)
contrast = ring - boat
status = "OK" if contrast >= MIN_CONTRAST else "FAIL"
print(f"p40-night boat={boat:.1f} ring={ring:.1f} contrast={contrast:.1f} (>= {MIN_CONTRAST:.0f}) {status}")
return 0 if contrast >= MIN_CONTRAST else 1
if __name__ == "__main__":
raise SystemExit(main(sys.argv))
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