split / pipeline /dedup.py
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"""Deduplication engine (global across all classes and queries).
Layer 1 exact SHA-256 of the original bytes (already the image_id, so identical downloads
collapse at download time) + SHA-256 of the decoded normalized pixels.
Layer 2 near-dup pHash AND dHash (64-bit each) within a Hamming-distance budget. Every image
also stores the hashes of its horizontally FLIPPED version, and a pair counts
as a duplicate if it matches in either orientation (mirror copies).
Layer 3 semantic CLIP-embedding cosine clustering. This layer never deletes anything; it only
merges cluster ids so the splitter keeps "same board, different angle" together.
Layers 1-2 remove images: within a duplicate group the keeper is chosen by
(already-processed before new) > (real-world before web) > higher resolution > larger file > id
so re-running the pipeline never swaps out an image that was already kept or annotated.
Duplicate groups are connected components (union-find), so chains A~B~C collapse into one group.
"""
from __future__ import annotations
import logging
from collections import defaultdict
from concurrent.futures import ThreadPoolExecutor, as_completed
from pathlib import Path
from typing import Sequence
import imagehash
import numpy as np
from PIL import Image, ImageOps
from tqdm import tqdm
from .manifest import Manifest
log = logging.getLogger(__name__)
# Statuses whose images are candidates for duplicate comparison (hashes present).
_PROCESSED = ("deduped", "kept", "review")
_CANDIDATES = ("normalized",) + _PROCESSED
_POP8 = np.array([bin(i).count("1") for i in range(256)], dtype=np.uint8)
# ------------------------------------------------------------------------------------ hashing
def compute_hashes(path: str | Path) -> dict[str, str]:
"""pHash/dHash (8x8 => 64 bit, hex) for an image and for its horizontal mirror."""
with Image.open(path) as im:
im.draft("RGB", (512, 512)) # cheap JPEG downscale on decode; same procedure for all images
im = ImageOps.exif_transpose(im).convert("RGB")
flipped = ImageOps.mirror(im)
return {
"phash": str(imagehash.phash(im, hash_size=8)),
"dhash": str(imagehash.dhash(im, hash_size=8)),
"phash_flip": str(imagehash.phash(flipped, hash_size=8)),
"dhash_flip": str(imagehash.dhash(flipped, hash_size=8)),
}
def hex_to_u64(values: Sequence[str]) -> np.ndarray:
return np.array([int(v, 16) for v in values], dtype=np.uint64)
def popcount64(x: np.ndarray) -> np.ndarray:
"""Per-element population count of a uint64 array."""
if hasattr(np, "bitwise_count"): # numpy >= 2.0
return np.bitwise_count(x)
x = np.ascontiguousarray(x)
return _POP8[x.view(np.uint8).reshape(*x.shape, 8)].sum(axis=-1)
# --------------------------------------------------------------------------------- union-find
class UnionFind:
def __init__(self, n: int):
self.parent = list(range(n))
def find(self, a: int) -> int:
while self.parent[a] != a:
self.parent[a] = self.parent[self.parent[a]]
a = self.parent[a]
return a
def union(self, a: int, b: int) -> None:
ra, rb = self.find(a), self.find(b)
if ra != rb:
self.parent[max(ra, rb)] = min(ra, rb)
def groups(self) -> list[list[int]]:
out: dict[int, list[int]] = defaultdict(list)
for i in range(len(self.parent)):
out[self.find(i)].append(i)
return [g for g in out.values() if len(g) > 1]
def near_duplicate_pairs(ph: np.ndarray, dh: np.ndarray, phf: np.ndarray, dhf: np.ndarray,
phash_max: int, dhash_max: int, block_cells: int = 4_000_000):
"""Yield (i, j), i < j, whose pHash *and* dHash are within budget in the same orientation
(direct, or with j mirrored). Vectorized in row blocks to bound memory."""
n = len(ph)
if n < 2:
return
block = max(1, block_cells // n)
cols = np.arange(n)
for a in range(0, n, block):
b = min(n, a + block)
upper = cols[None, :] > np.arange(a, b)[:, None]
direct = (popcount64(ph[a:b, None] ^ ph[None, :]) <= phash_max) & \
(popcount64(dh[a:b, None] ^ dh[None, :]) <= dhash_max)
mirrored = (popcount64(ph[a:b, None] ^ phf[None, :]) <= phash_max) & \
(popcount64(dh[a:b, None] ^ dhf[None, :]) <= dhash_max)
ii, jj = np.nonzero((direct | mirrored) & upper)
for i, j in zip(ii + a, jj):
yield int(i), int(j)
def find_duplicate_groups(rows: list[dict], phash_max: int, dhash_max: int) -> list[list[int]]:
"""Group row indices by exact pixel hash + near-duplicate hashes (connected components)."""
n = len(rows)
uf = UnionFind(n)
by_pixels: dict[str, int] = {}
for i, r in enumerate(rows):
px = r.get("pixel_sha256")
if px:
if px in by_pixels:
uf.union(by_pixels[px], i)
else:
by_pixels[px] = i
if n >= 2:
ph = hex_to_u64([r["phash"] for r in rows])
dh = hex_to_u64([r["dhash"] for r in rows])
phf = hex_to_u64([r["phash_flip"] for r in rows])
dhf = hex_to_u64([r["dhash_flip"] for r in rows])
for i, j in near_duplicate_pairs(ph, dh, phf, dhf, phash_max, dhash_max):
uf.union(i, j)
return uf.groups()
def keeper_rank(row: dict) -> tuple:
"""Lower sorts first = preferred keeper."""
processed = 0 if row["status"] in _PROCESSED else 1
realworld = 0 if row.get("origin") == "realworld" else 1
pixels = (row.get("norm_width") or row.get("width") or 0) * (row.get("norm_height") or row.get("height") or 0)
return (processed, realworld, -pixels, -(row.get("filesize") or 0), row["image_id"])
# ------------------------------------------------------------------------------------- stage
def run(manifest: Manifest, cfg: dict, data_dir: Path) -> dict[str, int]:
"""Hash new images, then discard exact/near duplicates across the whole candidate pool."""
dcfg = cfg["dedup"]
stats = {"hashed": 0, "exact_duplicate": 0, "near_duplicate": 0, "deduped": 0, "hash_failed": 0}
# 1. hashes for images that do not have them yet
fresh = [r for r in manifest.images(statuses=["normalized"]) if not r["phash"]]
if fresh:
def work(r: dict):
try:
return r, compute_hashes(data_dir / r["norm_path"]), None
except Exception as exc: # noqa: BLE001
return r, None, exc
with ThreadPoolExecutor(max_workers=int(dcfg.get("hash_workers", 4))) as ex:
futures = [ex.submit(work, r) for r in fresh]
with manifest.transaction():
for fut in tqdm(as_completed(futures), total=len(futures), desc="hash", unit="img"):
r, hashes, err = fut.result()
if err is not None:
log.warning("hashing failed for %s: %s", r["image_id"], err)
manifest.discard(r["image_id"], "hash_failed")
stats["hash_failed"] += 1
else:
manifest.update_image(r["image_id"], **hashes)
stats["hashed"] += 1
# 2. group duplicates over the full candidate pool (new + previously processed)
rows = [r for r in manifest.images(statuses=_CANDIDATES) if r["phash"]]
groups = find_duplicate_groups(rows, int(dcfg["phash_max_dist"]), int(dcfg["dhash_max_dist"]))
log.info("dedup: %d candidates, %d duplicate group(s)", len(rows), len(groups))
discarded: set[str] = set()
cluster_of: dict[str, str] = {} # cluster ids assigned during this run
with manifest.transaction():
for group in groups:
members = sorted((rows[i] for i in group), key=keeper_rank)
keeper, losers = members[0], members[1:]
# Reuse the keeper's existing cluster id: a previous semantic merge may have
# renamed it, and a rerun must never undo that.
cid = keeper["cluster_id"] or keeper["image_id"]
for member in members:
cluster_of[member["image_id"]] = cid
manifest.update_image(member["image_id"], cluster_id=cid)
for loser in losers:
exact = bool(loser["pixel_sha256"]) and loser["pixel_sha256"] == keeper["pixel_sha256"]
reason = "exact_duplicate" if exact else "near_duplicate"
if loser["status"] == "normalized":
manifest.discard(loser["image_id"], reason, dup_of=keeper["image_id"])
discarded.add(loser["image_id"])
stats[reason] += 1
else:
# An already-processed image is never removed retroactively (it may already
# be annotated); it only joins the cluster so splits stay leak-free.
log.warning("kept %s although it duplicates %s (already processed)",
loser["image_id"], keeper["image_id"])
# Survivors advance; singletons get their own cluster id.
for r in rows:
if r["status"] != "normalized" or r["image_id"] in discarded:
continue
updates = {"status": "deduped"}
if not cluster_of.get(r["image_id"]) and not r["cluster_id"]:
updates["cluster_id"] = r["image_id"]
manifest.update_image(r["image_id"], **updates)
stats["deduped"] += 1
log.info("dedup: %s", stats)
return stats
# ------------------------------------------------------------------------- semantic clustering
def semantic_clusters(ids: list[str], emb: np.ndarray, threshold: float,
existing: dict[str, str] | None = None, block_cells: int = 4_000_000) -> dict[str, str]:
"""Merge images into clusters by embedding cosine >= threshold (and by existing cluster ids).
Returns image_id -> cluster id (the smallest image_id in the component, deterministic).
Assumes rows of ``emb`` are L2-normalized.
"""
n = len(ids)
uf = UnionFind(n)
if existing:
first_seen: dict[str, int] = {}
for i, image_id in enumerate(ids):
cid = existing.get(image_id)
if cid:
if cid in first_seen:
uf.union(first_seen[cid], i)
else:
first_seen[cid] = i
if n >= 2:
block = max(1, block_cells // n)
cols = np.arange(n)
for a in range(0, n, block):
b = min(n, a + block)
sim = emb[a:b] @ emb.T
ii, jj = np.nonzero((sim >= threshold) & (cols[None, :] > np.arange(a, b)[:, None]))
for i, j in zip(ii + a, jj):
uf.union(int(i), int(j))
comp: dict[int, list[str]] = defaultdict(list)
for i, image_id in enumerate(ids):
comp[uf.find(i)].append(image_id)
return {image_id: min(members) for members in comp.values() for image_id in members}
def run_semantic(manifest: Manifest, cfg: dict) -> dict[str, int]:
"""Layer 3: merge cluster ids using stored CLIP embeddings (labels only, deletes nothing)."""
rows = manifest.images(statuses=["kept", "review"])
ids, emb = manifest.load_embeddings([r["image_id"] for r in rows])
if not ids:
log.warning("cluster: no embeddings found (run `filter` with CLIP first); skipping")
return {"clustered": 0, "merged_clusters": 0}
existing = {r["image_id"]: r["cluster_id"] or r["image_id"] for r in rows}
norms = np.linalg.norm(emb, axis=1, keepdims=True)
emb = emb / np.clip(norms, 1e-9, None)
new_ids = semantic_clusters(ids, emb, float(cfg["dedup"]["semantic_cosine"]), existing)
remap: dict[str, str] = {}
for image_id, new in new_ids.items():
old = existing[image_id]
if old != new:
remap[old] = new
with manifest.transaction():
# Update *all* rows (incl. discarded duplicates) that carry a merged cluster id.
for old, new in remap.items():
manifest.execute("UPDATE images SET cluster_id=? WHERE cluster_id=?", (new, old))
for image_id, new in new_ids.items():
if image_id not in remap and existing[image_id] != new:
manifest.update_image(image_id, cluster_id=new)
stats = {"clustered": len(ids), "merged_clusters": len(remap)}
log.info("cluster: %s", stats)
return stats