feat(scripts): fidelity_metrics.py + correct the qwen-vs-controlnet claim

Add scripts/fidelity_metrics.py: an objective eval harness comparing
watermark-removal outputs against the original (reference) across four groups
-- OCR character error rate (EasyOCR), ArcFace identity cosine (insightface),
face texture (LPIPS + Laplacian-variance ratio), and whole-image LPIPS/SSIM/
PSNR. PEP 723 inline deps so it stays out of the package / uv.lock; metrics
self-gate (faces only where faces, text only where text).

The metrics overturned an eyeball conclusion: at EQUAL strength Qwen beats
controlnet on TEXT (OpenAI typography 0.10: OCR CER 0.25 vs 0.37) but controlnet
beats Qwen on FACES (gemini_3, 18 faces, 0.15 each: Laplacian-variance retention
0.62 vs 0.41, face LPIPS 0.09 vs 0.13 -- Qwen smooths faces MORE; ArcFace
identity ~tied). So Qwen is the better TEXT-preserving remover, not a universal
fidelity win. Correct the earlier "qwen keeps faces faithful where controlnet
plasticizes" claim in CLAUDE.md, module-internals.md, known-limitations.md, README.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Victor Kuznetsov
2026-06-20 09:58:22 -07:00
parent 76e3d4154c
commit a2c33af284
5 changed files with 309 additions and 4 deletions
+303
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# /// script
# requires-python = ">=3.10"
# dependencies = [
# "click",
# "numpy",
# "opencv-python-headless",
# "pillow",
# "scikit-image",
# "rapidfuzz",
# "torch",
# "lpips",
# "easyocr",
# "insightface",
# "onnxruntime",
# ]
# ///
"""Objective fidelity metrics for comparing watermark-removal outputs.
Given an ORIGINAL (the reference) and one or more cleaned VARIANTS that have all
ALREADY passed the scrub oracle, this scores how much real detail each variant
preserved -- so "closer to the original" is the right axis here (between two
equally-scrubbed outputs, the one that deviates less from the original wins).
It is a standalone eval tool, NOT part of the package: PEP 723 inline deps let
``uv run`` build a throwaway env so the heavy models (EasyOCR, insightface,
LPIPS) never touch uv.lock or the shipped library. Metrics self-gate: face
metrics run only where faces are detected, text metrics only where text is.
Four metric groups (all reference = original):
1. Text -- EasyOCR character error rate (CER) of each variant vs the original's
OCR string. Lower = text better preserved. OCR is noisy, so treat it
as a RELATIVE comparison (every variant scored against the same ref).
2. Face identity -- insightface (buffalo_l) ArcFace cosine similarity, original
face vs the geometrically-matched variant face. Higher = identity kept.
3. Face texture -- LPIPS + Laplacian-variance ratio (variant/original) on face
crops. Catches "plastication" (lost high-frequency skin detail):
lapvar ratio < 1 = smoother than the original.
4. Whole image -- LPIPS / SSIM / PSNR vs the original (context: background too).
Usage:
uv run scripts/fidelity_metrics.py --original O.png \
--variant controlnet=C.png --variant qwen=Q.png --ocr-langs en,ru,ch_sim
"""
from __future__ import annotations
import logging
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any
import click
import cv2
import numpy as np
from _plain_console import Console, Table
logging.basicConfig(level=logging.WARNING, format="%(message)s")
log = logging.getLogger(__name__)
console = Console()
# ── helpers ──────────────────────────────────────────────────────────
def _load_bgr(path: str) -> np.ndarray:
img = cv2.imread(path, cv2.IMREAD_COLOR)
if img is None:
raise click.ClickException(f"cannot read image: {path}")
return img
def _match_size(variant: np.ndarray, ref: np.ndarray) -> np.ndarray:
"""Resize a variant to the reference size (outputs differ by a grid-round)."""
if variant.shape[:2] != ref.shape[:2]:
variant = cv2.resize(variant, (ref.shape[1], ref.shape[0]), interpolation=cv2.INTER_LANCZOS4)
return variant
# ── text: OCR CER ────────────────────────────────────────────────────
# EasyOCR rejects some language combos in one Reader, so group into compatible
# readers and union the detections. Cyrillic and Chinese cannot share a reader.
_OCR_GROUPS = {
"en": ["en"],
"ru": ["ru", "en"],
"ch_sim": ["ch_sim", "en"],
}
def _ocr_string(readers: list, bgr: np.ndarray) -> str:
"""Union all readers' detections into one position-sorted, whitespace-free string."""
rgb = cv2.cvtColor(bgr, cv2.COLOR_BGR2RGB)
dets: list[tuple[float, float, str]] = []
for reader in readers:
for box, text, conf in reader.readtext(rgb):
if conf < 0.3 or not text.strip():
continue
ys = [p[1] for p in box]
xs = [p[0] for p in box]
dets.append((min(ys), min(xs), text.strip()))
# Sort top-to-bottom, then left-to-right (coarse reading order).
dets.sort(key=lambda d: (round(d[0] / 20.0), d[1]))
return "".join(t for _, _, t in dets).replace(" ", "")
def _build_ocr_readers(langs: list[str]) -> list:
import easyocr
seen: set[tuple[str, ...]] = set()
readers = []
for lang in langs:
group = tuple(_OCR_GROUPS.get(lang, [lang]))
if group in seen:
continue
seen.add(group)
readers.append(easyocr.Reader(list(group), gpu=False, verbose=False))
return readers
# ── face: detection + ArcFace + texture ──────────────────────────────
@dataclass
class FaceStats:
n_faces: int = 0
identity: list[float] = field(default_factory=list)
lpips: list[float] = field(default_factory=list)
lapvar_ratio: list[float] = field(default_factory=list)
def _lap_var(bgr: np.ndarray) -> float:
gray = cv2.cvtColor(bgr, cv2.COLOR_BGR2GRAY)
return float(cv2.Laplacian(gray, cv2.CV_64F).var())
def _match_face(orig_face: Any, variant_faces: list[Any]) -> Any:
"""Nearest variant face to an original face by bbox-center distance (geometry kept)."""
ox, oy = (orig_face.bbox[0] + orig_face.bbox[2]) / 2, (orig_face.bbox[1] + orig_face.bbox[3]) / 2
best, best_d = None, 1e18
for vf in variant_faces:
vx, vy = (vf.bbox[0] + vf.bbox[2]) / 2, (vf.bbox[1] + vf.bbox[3]) / 2
d = (ox - vx) ** 2 + (oy - vy) ** 2
if d < best_d:
best, best_d = vf, d
return best
def _cosine(a: np.ndarray, b: np.ndarray) -> float:
return float(np.dot(a, b) / (np.linalg.norm(a) * np.linalg.norm(b) + 1e-9))
def _crop(bgr: np.ndarray, bbox: Any) -> np.ndarray:
h, w = bgr.shape[:2]
x1, y1, x2, y2 = (int(max(0, bbox[0])), int(max(0, bbox[1])), int(min(w, bbox[2])), int(min(h, bbox[3])))
return bgr[y1:y2, x1:x2]
# ── whole image: LPIPS / SSIM / PSNR ─────────────────────────────────
def _lpips_model() -> tuple[Any, Any]:
import lpips
import torch
model = lpips.LPIPS(net="alex", verbose=False)
model.eval()
return model, torch
def _lpips_distance(model_torch: tuple[Any, Any], a_bgr: np.ndarray, b_bgr: np.ndarray) -> float:
model, torch = model_torch
def _t(img: np.ndarray) -> Any:
rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB).astype(np.float32) / 127.5 - 1.0
return torch.from_numpy(rgb).permute(2, 0, 1).unsqueeze(0)
with torch.no_grad():
return float(model(_t(a_bgr), _t(b_bgr)).item())
def _ssim_psnr(a_bgr: np.ndarray, b_bgr: np.ndarray) -> tuple[float, float]:
from skimage.metrics import peak_signal_noise_ratio, structural_similarity
a = cv2.cvtColor(a_bgr, cv2.COLOR_BGR2GRAY)
b = cv2.cvtColor(b_bgr, cv2.COLOR_BGR2GRAY)
ssim = float(structural_similarity(a, b))
psnr = float(peak_signal_noise_ratio(a, b))
return ssim, psnr
# ── main ─────────────────────────────────────────────────────────────
def _mean(xs: list[float]) -> float | None:
return sum(xs) / len(xs) if xs else None
def _fmt(v: float | None, nd: int = 3) -> str:
return "-" if v is None else f"{v:.{nd}f}"
@click.command()
@click.option("--original", required=True, type=click.Path(exists=True), help="Reference (unprocessed) image.")
@click.option(
"--variant",
"variants",
multiple=True,
required=True,
help="LABEL=PATH of a cleaned output (repeatable).",
)
@click.option("--ocr-langs", default="en", help="Comma list of EasyOCR langs (en,ru,ch_sim). Empty = skip text.")
@click.option("--no-faces", is_flag=True, help="Skip face metrics.")
def main(original: str, variants: tuple[str, ...], ocr_langs: str, no_faces: bool) -> None:
"""Score each VARIANT against ORIGINAL across the four fidelity groups."""
ref = _load_bgr(original)
parsed: list[tuple[str, np.ndarray]] = []
for spec in variants:
if "=" not in spec:
raise click.ClickException(f"--variant must be LABEL=PATH, got {spec!r}")
label, path = spec.split("=", 1)
parsed.append((label, _match_size(_load_bgr(path), ref)))
langs = [x.strip() for x in ocr_langs.split(",") if x.strip()]
lp = _lpips_model() # AlexNet LPIPS, loaded once and reused for face crops + whole image
# ── text ──
ocr_cer: dict[str, float | None] = {label: None for label, _ in parsed}
if langs:
console.print(f" OCR ({','.join(langs)})...")
from rapidfuzz.distance import Levenshtein
readers = _build_ocr_readers(langs)
ref_text = _ocr_string(readers, ref)
if ref_text:
for label, img in parsed:
hyp = _ocr_string(readers, img)
ocr_cer[label] = Levenshtein.normalized_distance(ref_text, hyp)
else:
console.print(" (no text detected in the original; skipping text metric)")
# ── faces ──
face_stats: dict[str, FaceStats] = {label: FaceStats() for label, _ in parsed}
if not no_faces:
console.print(" Faces (insightface buffalo_l)...")
from insightface.app import FaceAnalysis
app = FaceAnalysis(name="buffalo_l", providers=["CPUExecutionProvider"])
app.prepare(ctx_id=-1, det_size=(640, 640))
ref_faces = app.get(ref)
if ref_faces:
for label, img in parsed:
vfaces = app.get(img)
st = face_stats[label]
for of in ref_faces:
vf = _match_face(of, vfaces)
if vf is None:
continue
st.n_faces += 1
st.identity.append(_cosine(of.normed_embedding, vf.normed_embedding))
oc, vc = _crop(ref, of.bbox), _crop(img, of.bbox)
if oc.size == 0 or vc.size == 0:
continue
vc_r = cv2.resize(vc, (oc.shape[1], oc.shape[0]), interpolation=cv2.INTER_LANCZOS4)
st.lpips.append(_lpips_distance(lp, oc, vc_r))
ov = _lap_var(oc)
st.lapvar_ratio.append(_lap_var(vc_r) / ov if ov > 1e-6 else 0.0)
else:
console.print(" (no faces detected in the original; skipping face metrics)")
# ── whole image ──
console.print(" Whole-image LPIPS/SSIM/PSNR...")
whole: dict[str, tuple[float, float, float]] = {}
for label, img in parsed:
ssim, psnr = _ssim_psnr(ref, img)
whole[label] = (_lpips_distance(lp, ref, img), ssim, psnr)
# ── report ──
table = Table(title=f"Fidelity vs {Path(original).name} (reference)")
for col in ("variant", "text CER↓", "faces", "ID cos↑", "face LPIPS↓", "lapvar↑", "img LPIPS↓", "SSIM↑", "PSNR↑"):
table.add_column(col)
for label, _ in parsed:
st = face_stats[label]
wl, ws, wp = whole[label]
table.add_row(
label,
_fmt(ocr_cer[label]),
str(st.n_faces),
_fmt(_mean(st.identity)),
_fmt(_mean(st.lpips)),
_fmt(_mean(st.lapvar_ratio)),
_fmt(wl),
_fmt(ws),
_fmt(wp, 1),
)
console.print(table)
console.print(
" Legend: CER lower=better; ID cos higher=better; face LPIPS lower=better; "
"lapvar ratio ~1=detail kept, <1=smoothed/plastic; img LPIPS lower=better; SSIM/PSNR higher=closer."
)
if __name__ == "__main__":
main()