#!/usr/bin/env python3
from pathlib import Path
from PIL import Image, ImageChops, ImageStat

ROOT = Path(__file__).resolve().parent
baseline_path = ROOT / "rendered/resizes-content-baseline.png"
expected_path = ROOT / "expected/resizes-content-patched.png"
diff_path = ROOT / "diff/resizes-content.png"

baseline = Image.open(baseline_path).convert("RGB")
expected = Image.open(expected_path).convert("RGB")
if baseline.size != expected.size:
    raise SystemExit(f"size mismatch: {baseline.size} != {expected.size}")

raw = ImageChops.difference(baseline, expected)
stat = ImageStat.Stat(raw)
rms = sum(value * value for value in stat.rms) ** 0.5
mask = raw.convert("L").point(lambda value: 255 if value > 24 else 0)
overlay = expected.copy()
red = Image.new("RGB", expected.size, (211, 95, 95))
overlay.paste(red, mask=mask)
overlay = Image.blend(expected, overlay, 0.65)
diff_path.parent.mkdir(parents=True, exist_ok=True)
overlay.save(diff_path)
changed = sum(mask.histogram()[1:]) / (baseline.width * baseline.height)
print(f"size={baseline.width}x{baseline.height}")
print(f"changed_ratio={changed:.6f}")
print(f"combined_rms={rms:.3f}")
print(f"wrote={diff_path}")