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remove-ai-watermarks/scripts/synthid_v3_codebook_probe.py
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Python

"""Independently evaluate a numeric reverse-SynthID V3 NPZ codebook.
The loader accepts only the documented dense or sparse numeric format-v2 arrays
and disables pickle. It does not import or execute third-party code. Scores are
exploratory: the external reference provenance and labels still require
independent oracle validation before this can support a SynthID detector claim.
"""
from __future__ import annotations
import json
import logging
from dataclasses import asdict, dataclass
from pathlib import Path
import click
import numpy as np
from PIL import Image
from synthid_phase_registration import (
MAX_TRANSLATION_SHIFT,
extract_frequency_values,
phase_adjustment,
register_phase_translations,
)
log = logging.getLogger(__name__)
LOG_2 = np.log(2.0)
@dataclass(frozen=True)
class V3CarrierModel:
"""Selected numeric bins from one exact-resolution V3 profile."""
height: int
width: int
rows: np.ndarray
columns: np.ndarray
channels: np.ndarray
phases: np.ndarray
weights: np.ndarray
expected_magnitudes: np.ndarray
@dataclass(frozen=True)
class V3Score:
"""Phase-alignment scores for one image."""
path: str
phase_score: float
axial_phase_score: float
active_weight_fraction: float
peak_count: int
@dataclass(frozen=True)
class V3RegisteredScore:
"""Best phase-alignment score across a bounded translation search."""
path: str
phase_score: float
axial_phase_score: float
active_weight_fraction: float
peak_count: int
row_shift: int
column_shift: int
@dataclass(frozen=True)
class _CarrierCandidates:
"""Selected numeric carrier arrays from one V3 profile."""
weights: np.ndarray
rows: np.ndarray
columns: np.ndarray
channels: np.ndarray
phases: np.ndarray
magnitudes: np.ndarray
def _load_sparse_channel(artifact: np.lib.npyio.NpzFile, prefix: str, channel: int) -> tuple[np.ndarray, ...]:
"""Load one sparse channel without reconstructing full image-sized arrays."""
indices = np.asarray(artifact[f"{prefix}idx_{channel}"], dtype=np.uint32)
log_magnitudes = np.asarray(artifact[f"{prefix}mag_{channel}"])
phases = np.asarray(artifact[f"{prefix}phase_{channel}"])
coherence = np.asarray(artifact[f"{prefix}cons_{channel}"], dtype=np.float64) / 255.0
if not (indices.shape == log_magnitudes.shape == phases.shape == coherence.shape):
raise ValueError("sparse profile arrays have inconsistent shapes")
return indices, log_magnitudes, phases, coherence
def _top_positions(selection: np.ndarray, tie_breaker: np.ndarray, peak_count: int) -> np.ndarray:
"""Return deterministic descending positions for the strongest candidates."""
if len(selection) < peak_count:
raise ValueError(f"profile exposes only {len(selection)} eligible bins")
cutoff = np.partition(selection, -peak_count)[-peak_count]
stronger = np.flatnonzero(selection > cutoff)
tied = np.flatnonzero(selection == cutoff)
remaining = peak_count - len(stronger)
if remaining < len(tied):
tied = tied[np.argpartition(tie_breaker[tied], -remaining)[-remaining:]]
positions = np.concatenate((stronger, tied))
order = np.lexsort((-tie_breaker[positions], -selection[positions]))
return positions[order]
def _dense_candidates(
artifact: np.lib.npyio.NpzFile,
prefix: str,
*,
height: int,
width: int,
min_radius: float,
peak_count: int,
) -> _CarrierCandidates:
"""Select candidate arrays from one dense numeric profile."""
shape = (height, width // 2 + 1, 3)
log_magnitudes = np.asarray(artifact[f"{prefix}mag"])
phases = np.asarray(artifact[f"{prefix}phase"])
coherence = np.asarray(artifact[f"{prefix}cons"], dtype=np.float64) / 255.0
if not (log_magnitudes.shape == phases.shape == coherence.shape == shape):
raise ValueError("dense profile arrays have inconsistent shapes")
rows = np.arange(height)
signed_rows = np.where(rows > height // 2, rows - height, rows)
columns = np.arange(shape[1])
radius = np.sqrt(np.square(signed_rows[:, None]) + np.square(columns[None, :]))
valid_spatial = (radius >= min_radius) & (columns[None, :] > 0)
valid = np.broadcast_to(valid_spatial[:, :, None], shape)
flat_valid = np.flatnonzero(valid)
selection = (np.square(coherence) * log_magnitudes * LOG_2).ravel()[flat_valid]
positions = _top_positions(selection, flat_valid, peak_count)
selected = flat_valid[positions]
selected_rows, selected_columns, selected_channels = np.unravel_index(selected, shape)
return _CarrierCandidates(
weights=selection[positions],
rows=selected_rows,
columns=selected_columns,
channels=selected_channels,
phases=np.asarray(phases.ravel()[selected], dtype=np.float64),
magnitudes=np.exp2(np.asarray(log_magnitudes.ravel()[selected], dtype=np.float64)) - 1.0,
)
def _sparse_candidates(
artifact: np.lib.npyio.NpzFile,
prefix: str,
*,
height: int,
width: int,
min_radius: float,
peak_count: int,
) -> _CarrierCandidates:
"""Select candidate arrays from one sparse numeric profile."""
half_width = width // 2 + 1
selections: list[np.ndarray] = []
candidate_rows: list[np.ndarray] = []
candidate_columns: list[np.ndarray] = []
candidate_channels: list[np.ndarray] = []
candidate_phases: list[np.ndarray] = []
candidate_log_magnitudes: list[np.ndarray] = []
for channel in range(3):
indices, log_magnitudes, phases, coherence = _load_sparse_channel(artifact, prefix, channel)
rows, columns = np.unravel_index(indices, (height, half_width))
signed_rows = np.where(rows > height // 2, rows - height, rows)
radius = np.sqrt(np.square(signed_rows) + np.square(columns))
valid = (radius >= min_radius) & (columns > 0)
selections.append((np.square(coherence) * log_magnitudes * LOG_2)[valid])
candidate_rows.append(rows[valid])
candidate_columns.append(columns[valid])
candidate_channels.append(np.full(np.count_nonzero(valid), channel, dtype=np.int8))
candidate_phases.append(phases[valid])
candidate_log_magnitudes.append(log_magnitudes[valid])
selection = np.concatenate(selections)
rows = np.concatenate(candidate_rows)
columns = np.concatenate(candidate_columns)
channels = np.concatenate(candidate_channels)
tie_breaker = np.ravel_multi_index((rows, columns, channels), (height, half_width, 3))
selected = _top_positions(selection, tie_breaker, peak_count)
return _CarrierCandidates(
weights=selection[selected],
rows=rows[selected],
columns=columns[selected],
channels=channels[selected],
phases=np.asarray(np.concatenate(candidate_phases)[selected], dtype=np.float64),
magnitudes=np.exp2(np.asarray(np.concatenate(candidate_log_magnitudes)[selected], dtype=np.float64)) - 1.0,
)
def load_v3_model(
path: Path,
*,
height: int,
width: int,
peak_count: int = 256,
min_radius: float = 15.0,
) -> V3CarrierModel:
"""Load top phase-consistent bins from a numeric V3 codebook profile."""
prefix = f"{height}x{width}/"
with np.load(path, allow_pickle=False) as artifact:
if int(artifact["format_version"]) != 2:
raise ValueError("only numeric V3 format version 2 is supported")
loader = _sparse_candidates if bool(int(artifact[f"{prefix}sparse"])) else _dense_candidates
candidates = loader(
artifact,
prefix,
height=height,
width=width,
min_radius=min_radius,
peak_count=peak_count,
)
return V3CarrierModel(
height=height,
width=width,
rows=np.asarray(candidates.rows, dtype=np.int32),
columns=np.asarray(candidates.columns, dtype=np.int32),
channels=np.asarray(candidates.channels, dtype=np.int8),
phases=candidates.phases,
weights=candidates.weights / np.sum(candidates.weights),
expected_magnitudes=candidates.magnitudes,
)
def _load_profile_rgb(path: Path, model: V3CarrierModel) -> np.ndarray:
"""Load PATH and resize only when it does not match the profile geometry."""
with Image.open(path) as source:
image = source.convert("RGB")
if image.size != (model.width, model.height):
image = image.resize((model.width, model.height), Image.Resampling.LANCZOS)
return np.asarray(image, dtype=np.float64)
def _frequency_values(path: Path, model: V3CarrierModel) -> np.ndarray:
"""Return the selected complex coefficients from PATH."""
pixels = _load_profile_rgb(path, model)
return extract_frequency_values(pixels, model.rows, model.columns, model.channels)
def _score_values(
values: np.ndarray,
model: V3CarrierModel,
phase_offsets: np.ndarray | float = 0.0,
) -> tuple[float, float, float]:
"""Return phase, axial-phase, and active-weight scores for VALUES."""
phase_difference = np.angle(values) - model.phases
magnitude_gate = np.minimum(np.abs(values) / (model.expected_magnitudes + 1e-12), 1.0)
active_weights = model.weights * magnitude_gate
active_weight = float(np.sum(active_weights))
if active_weight == 0.0:
phase_score = 0.0
axial_score = 0.0
else:
adjusted = phase_difference + phase_offsets
phase_score = float(np.sum(active_weights * np.cos(adjusted)) / active_weight)
axial_score = float(np.sum(active_weights * np.cos(2.0 * adjusted)) / active_weight)
return phase_score, axial_score, active_weight
def score_image(path: Path, model: V3CarrierModel) -> V3Score:
"""Score PATH against selected V3 phase bins."""
phase_score, axial_score, active_weight = _score_values(_frequency_values(path, model), model)
return V3Score(
path=str(path),
phase_score=phase_score,
axial_phase_score=axial_score,
active_weight_fraction=active_weight,
peak_count=len(model.rows),
)
def score_translations(path: Path, model: V3CarrierModel, *, max_shift: int = 4) -> V3RegisteredScore:
"""Return the best score after compensating bounded integer translations."""
values = _frequency_values(path, model)
registration = register_phase_translations(
values,
phases=model.phases,
weights=model.weights,
expected_magnitudes=model.expected_magnitudes,
rows=model.rows,
columns=model.columns,
height=model.height,
width=model.width,
max_shift=max_shift,
)
selected_adjustment = phase_adjustment(
model.rows,
model.columns,
height=model.height,
width=model.width,
row_shift=registration.row_shift,
column_shift=registration.column_shift,
)
phase_score, axial_score, active_weight = _score_values(values, model, selected_adjustment)
return V3RegisteredScore(
path=str(path),
phase_score=phase_score,
axial_phase_score=axial_score,
active_weight_fraction=active_weight,
peak_count=len(model.rows),
row_shift=registration.row_shift,
column_shift=registration.column_shift,
)
@click.command()
@click.argument("codebook", type=click.Path(exists=True, dir_okay=False, path_type=Path))
@click.argument("images", nargs=-1, required=True, type=click.Path(exists=True, dir_okay=False, path_type=Path))
@click.option("--height", type=click.IntRange(min=64), required=True)
@click.option("--width", type=click.IntRange(min=64), required=True)
@click.option("--peak-count", type=click.IntRange(min=1), default=256, show_default=True)
@click.option("--max-shift", type=click.IntRange(min=0, max=MAX_TRANSLATION_SHIFT), default=0, show_default=True)
@click.option("--report-out", type=click.Path(dir_okay=False, path_type=Path), required=True)
def main(
codebook: Path,
images: tuple[Path, ...],
height: int,
width: int,
peak_count: int,
max_shift: int,
report_out: Path,
) -> None:
"""Score IMAGES against one exact-resolution profile from CODEBOOK."""
model = load_v3_model(codebook, height=height, width=width, peak_count=peak_count)
scores = (
[asdict(score_image(image, model)) for image in images]
if max_shift == 0
else [asdict(score_translations(image, model, max_shift=max_shift)) for image in images]
)
payload = {
"codebook": str(codebook),
"height": height,
"width": width,
"peak_count": peak_count,
"max_shift": max_shift,
"scores": scores,
}
report_out.parent.mkdir(parents=True, exist_ok=True)
report_out.write_text(json.dumps(payload, indent=2) + "\n", encoding="utf-8")
log.info("Wrote V3 score report: %s", report_out)
if __name__ == "__main__":
logging.basicConfig(level=logging.INFO, format="%(message)s")
main()