BLIP3o-Recap / code /recaption.py
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"""Recaption BLIP3o-Recap webdataset shards with Qwen2.5-VL-3B-Instruct (vLLM, one process per GPU).
Each image keeps its original caption and gets two new ones; one jsonl per shard with
``{key, source_shard, orig_caption, recap_1, recap_2}``. Rejected samples (see ``violations``) are resampled.
Resumable: keys already in a shard's jsonl are skipped and finished shards have a ``.done`` marker.
python recaption.py run --shards data/*.tar --out out/ [--limit 1000] [--focus]
python recaption.py stats out/*.jsonl [--sim 500]
python recaption.py export --src out/ --out hf/recaptions --manifest subset_manifest.json # needs pyarrow
"""
import argparse
import io
import json
import os
import random
import re
import tarfile
import time
from concurrent.futures import ThreadPoolExecutor
from pathlib import Path
MODEL = "Qwen/Qwen2.5-VL-3B-Instruct"
MAX_PIXELS = 640 * 28 * 28
SYSTEM = "You are an image captioner. Describe only what is visible."
USER = """Describe this image in ONE paragraph of 70–90 words.
Order: main subject(s) (count, category, color, size, pose/action) → spatial relations (left/right, front/behind, near/far) → background and setting → lighting, viewpoint, and medium (photo, illustration, 3D render, etc.).
Rules:
- Start directly with the main subject. Never begin with "The image", "This picture", "In this photo", or similar.
- State only what is clearly visible. No guesses ("likely", "possibly", "suggesting", "appears to be"), no mood words ("serene", "vibrant", "charming", "picturesque"), no interpretation of purpose or meaning.
- Quote visible text only if it is legible.
- No lists, no line breaks, no concluding summary sentence."""
# --focus: appended to the second caption's prompt only, so the two captions differ in emphasis
FOCUS = "\nPut extra emphasis on colors, materials, and attributes of each object rather than on the layout."
# Decode-time ban of the filtered phrases (the prompt is kept verbatim): without it, Qwen2.5-VL-3B starts ~60% of
# captions with "The image ..." and uses one of the banned words in ~80%, so resampling alone cannot fix them.
# Openers go through vLLM bad_words (multi-token, works); words through logit_bias (see ban_bias).
_SPEC = ("likely", "possibly", "appears", "suggesting", "serene", "vibrant", "charming", "picturesque")
# beyond the spec list: inflections and the substitutes the model switches to once the spec words are banned
_EXTRA = ("appear", "appeared", "appearing", "suggest", "suggests", "suggested", "seem", "seems", "seemed", "seemingly",
"indicating", "indicates", "indicate", "indicated", "indicative", "perhaps", "probably", "might", "possible",
"tranquil", "peaceful", "idyllic", "cozy", "inviting", "stunning", "breathtaking", "bustling",
"overall", "atmosphere", "ambiance", "ambience", # summary sentences ("The overall ...") and mood
# second round, from word counts on the first 177k full-run captions
"calm", "lively", "festive", "scenic", "striking", "dramatic", "majestic", "grand", "dynamic", "typical",
"emphasizing", "emphasizes", "emphasize", "emphasized", "enjoy", "enjoys", "enjoying", "welcoming",
"relaxed", "relaxing", "pleasant", "playful", "harmonious", "elegant", "whimsical", "energetic", "cheerful",
"celebratory", "celebrating", "intimate", "aesthetic", "iconic", "mood", "moody",
# third round (fixed after the full run with `fix`): guesses that still leaked
"potentially", "presumably", "apparently", "supposedly", "hinting", "hints", "implies", "implying",
"impression")
# interpretive phrases ("creating a sense of calm"), banned through bad_words like the openers
_PHRASES = ["creating a", "sense of", "giving a", "giving it", "giving the scene", "giving the image", "adding a",
"natural beauty", "looks like", "look like", "what looks", "could be", "may be"]
_WORDS = _SPEC + _EXTRA
_OPENERS = [f"{a} {b}" for a in ("The", "This", "These") for b in
("image", "picture", "photo", "photograph", "scene", "illustration", "snapshot")] + ["In this", "In the image",
"In the picture", "In the photo"]
# caption-initial "The"/"This"/"These" (no leading space: a different token from mid-sentence " The"); the model
# otherwise dodges every banned opener with "The main object in the image is ...", "The mainsubject ...", etc.
_FIRST = ("The", "This", "These")
def ban_bias(tokenizer) -> dict[int, float]:
"""logit_bias -100 on every single-token form of _WORDS (" vibrant", "Appear", ...).
vLLM's ``bad_words`` cannot ban them: it keeps the space-prefixed form only when it tokenizes to as many tokens
as the bare word, and e.g. "vibrant" is v|ibr|ant while " vibrant" is one token, so mid-sentence uses pass.
Rare multi-token forms (sentence-initial "Vibrant") are left to the filter.
"""
forms = [p + c for x in _WORDS for c in (x, x.capitalize()) for p in ("", " ")]
ids = [tokenizer.encode(f, add_special_tokens=False) for f in forms]
ids += [tokenizer.encode(f, add_special_tokens=False) for f in _FIRST]
return {i[0]: -100.0 for i in ids if len(i) == 1}
_OPENER = re.compile(
r"^\W*(?:(?:the|this|these)\s+(?:image|picture|photo|photograph|scene|illustration|snapshot)s?\b"
r"|in\s+(?:this|the)\s+(?:image|picture|photo|photograph|scene|illustration)\b)",
re.I,
)
_OPENER_X = re.compile(r"^\W*the\s+main", re.I)
_BANNED = re.compile(rf"\b(?:{'|'.join(_SPEC)})\b", re.I)
_BANNED_X = re.compile(rf"\b(?:{'|'.join(_EXTRA + tuple(_PHRASES))})\b", re.I)
_LIST = re.compile(r"(?:^|\n)\s*(?:[-*•]|\d+[.)])\s")
# CJK / kana / Hangul outside quotes: the model drifting into Chinese ("piles of salt结晶"); quoted signage is kept
_CJK = re.compile(r"[぀-ヿ㐀-䶿一-鿿가-힯]")
_QUOTED = re.compile(r"\"[^\"]*\"|“[^”]*”|「[^」]*」|'[^']*'")
def cap(text: str, finished: bool = True, max_words: int | None = None) -> str:
"""Drop a cut-off last sentence; with ``max_words``, also keep only the whole sentences that fit."""
sents = re.split(r"(?<=[.!?])\s+", text.strip())
if not finished or not sents[-1].endswith((".", "!", "?", '"')):
sents = sents[:-1]
out, n = [], 0
for x in sents:
n += len(x.split())
if max_words and n > max_words:
break
out.append(x)
return " ".join(out)
def violations(text: str, finished: bool = True, strict: bool = True) -> list[str]:
"""Reasons a caption is rejected (empty list = accepted); ``strict=False``: the spec rules only."""
out = []
if _OPENER.search(text) or strict and _OPENER_X.search(text):
out.append("opener")
bare = _QUOTED.sub("", text) # quoted visible text ("Enjoy the simple things") is kept verbatim
if _BANNED.search(bare) or strict and _BANNED_X.search(bare):
out.append("banned_word")
if "\n" in text.strip() or _LIST.search(text):
out.append("newline_list")
if _CJK.search(bare):
out.append("lang_drift")
if len(text.split()) < 60: # no upper bound: max_tokens=160 keeps it far below BERT's 512 tokens
out.append("length")
if not finished:
out.append("truncated")
return out
def prompt(focus: bool) -> str:
return (
f"<|im_start|>system\n{SYSTEM}<|im_end|>\n<|im_start|>user\n<|vision_start|><|image_pad|><|vision_end|>"
f"{USER}{FOCUS if focus else ''}<|im_end|>\n<|im_start|>assistant\n"
)
def read_shard(path: Path):
"""Yield ``(key, jpg bytes, caption)`` from a webdataset tar (members of a key are adjacent)."""
cur, parts = None, {}
with tarfile.open(path, "r|*") as tar:
for m in tar:
if not m.isfile():
continue
key, ext = m.name.rsplit(".", 1)
if key != cur:
if cur is not None and "jpg" in parts:
yield cur, parts["jpg"], parts.get("txt", b"").decode("utf-8", "replace").strip()
cur, parts = key, {}
parts[ext] = tar.extractfile(m).read()
if cur is not None and "jpg" in parts:
yield cur, parts["jpg"], parts.get("txt", b"").decode("utf-8", "replace").strip()
def load_image(data: bytes):
"""Decode and shrink to at most MAX_PIXELS so the processor's own resize is cheap."""
from PIL import Image
im = Image.open(io.BytesIO(data))
if im.width * im.height > 4 * MAX_PIXELS: # JPEG DCT-domain downscale, much faster than a full decode
im.draft("RGB", (im.width // 2, im.height // 2))
im = im.convert("RGB")
s = (MAX_PIXELS / (im.width * im.height)) ** 0.5
if s < 1:
im = im.resize((max(28, round(im.width * s)), max(28, round(im.height * s))), Image.BICUBIC)
return im
def claim(out: Path, shard: Path) -> bool:
if (out / f"{shard.stem}.done").exists():
return False
try:
os.close(os.open(out / f"{shard.stem}.lock", os.O_CREAT | os.O_EXCL))
return True
except FileExistsError:
return False
def _patch_bad_words() -> None:
"""Ban both the bare and the space-prefixed token sequence of every bad word.
vLLM keeps the space-prefixed variant only when it has as many tokens as the bare word, so mid-sentence
" giving a" (bare g|iving| a) or " whimsical" (bare wh|ims|ical) were never banned. The bad_words kernel itself
handles any token sequence; only this expansion (run in the frontend process) is replaced.
"""
from vllm import SamplingParams
def update_from_tokenizer(self, tokenizer) -> None:
if not self.bad_words:
return
ids = []
for w in self.bad_words:
for prefix in ("", " "):
t = tokenizer.encode(prefix + w.lstrip(), add_special_tokens=False)
if t and t not in ids:
ids.append(t)
self._bad_words_token_ids = ids
SamplingParams.update_from_tokenizer = update_from_tokenizer
def engine(args):
os.environ.setdefault("VLLM_MAX_NUM_BAD_WORDS", "1024") # ~400 sequences with every word form
os.environ.setdefault("VLLM_MAX_BAD_WORDS_TOTAL_TOKENS", "4096")
from vllm import LLM, SamplingParams
_patch_bad_words()
llm = LLM(
model=args.model,
max_model_len=2048,
gpu_memory_utilization=args.gpu_mem,
enable_prefix_caching=True,
limit_mm_per_prompt={"image": 1},
mm_processor_kwargs={"max_pixels": MAX_PIXELS},
seed=args.seed,
)
words = [c for x in _WORDS for c in (x, x.capitalize())] # multi-token forms; logit_bias covers single tokens
ban = {"bad_words": _OPENERS + _PHRASES + words, "logit_bias": ban_bias(llm.get_tokenizer())}
ban = {} if args.no_ban else ban
sp = lambda n: SamplingParams(n=n, temperature=0.8, top_p=0.9, max_tokens=160, **ban) # noqa: E731
return llm, sp
def run(args):
out = Path(args.out)
out.mkdir(parents=True, exist_ok=True)
llm, sp = engine(args)
pool = ThreadPoolExecutor(args.workers)
rank = os.environ.get("CUDA_VISIBLE_DEVICES", "0")
for shard in map(Path, args.shards):
if not claim(out, shard):
continue
dst = out / f"{shard.stem}.jsonl"
seen = {json.loads(l)["key"] for l in open(dst)} if dst.exists() else set()
stats = {"images": 0, "samples": 0, "rejected": 0, "reasons": {}, "fallback": [], "gen_s": 0.0}
sp_path = out / f"{shard.stem}.stats.json"
if sp_path.exists() and seen:
stats = json.load(open(sp_path))
t0, done = time.time(), len(seen)
items = ((k, j, c) for k, j, c in read_shard(shard) if k not in seen)
with open(dst, "a") as f:
while True:
chunk = [x for _, x in zip(range(args.chunk), items)]
if args.limit:
chunk = chunk[: max(0, args.limit - done)]
if not chunk:
break
imgs = list(pool.map(lambda x: load_image(x[1]), chunk))
tg = time.time()
rows = recaption(llm, sp, imgs, args.focus, args.retries, stats)
stats["gen_s"] += time.time() - tg
for (key, _, cap), (r1, r2, ok) in zip(chunk, rows):
f.write(json.dumps({"key": key, "source_shard": shard.name, "orig_caption": cap,
"recap_1": r1, "recap_2": r2}) + "\n")
if not ok:
stats["fallback"].append(key)
f.flush()
done += len(chunk)
stats["images"] = done
json.dump(stats, open(sp_path, "w"))
print(f"[gpu{rank}] {shard.name} {done} imgs {len(chunk) / (time.time() - tg + 1e-9):.1f} img/s "
f"(chunk) rej {stats['rejected'] / max(1, stats['samples']):.3f}", flush=True)
if args.limit and done >= args.limit:
break
stats["wall_s"] = stats.get("wall_s", 0) + time.time() - t0
json.dump(stats, open(sp_path, "w"))
if not args.limit:
(out / f"{shard.stem}.done").touch()
(out / f"{shard.stem}.lock").unlink(missing_ok=True)
def recaption(llm, sp, imgs, focus, retries, stats, todo=None):
"""Two accepted captions per image; resample rejected ones up to ``retries`` times, then keep the best.
``todo``: the ``(image, slot)`` pairs to generate (default: both slots of every image); others come back None.
"""
good = [[[], []] for _ in imgs] # per image, per slot (recap_1 / recap_2): accepted texts
best = [[None, None] for _ in imgs] # fallback: (n violations, text) with fewest violations
# slot 0 and slot 1 share the same prompt unless --focus, in which case slot 1 gets the FOCUS sentence
todo = todo or [(i, s) for i in range(len(imgs)) for s in (0, 1)]
asked = set(todo)
for attempt in range(retries + 1):
if not todo:
break
reqs, owners = [], []
if focus:
for i, s in todo:
reqs.append(({"prompt": prompt(s == 1), "multi_modal_data": {"image": imgs[i]}}, 1))
owners.append([(i, s)])
else: # one request per image with n = number of missing slots, so both samples share the prefill
by_img = {}
for i, s in todo:
by_img.setdefault(i, []).append(s)
for i, slots in by_img.items():
reqs.append(({"prompt": prompt(False), "multi_modal_data": {"image": imgs[i]}}, len(slots)))
owners.append([(i, s) for s in slots])
by_n = {}
for k, (_, n) in enumerate(reqs):
by_n.setdefault(n, []).append(k)
outs = [None] * len(reqs)
for n, ks in by_n.items():
for k, o in zip(ks, llm.generate([reqs[k][0] for k in ks], sp(n), use_tqdm=False)):
outs[k] = o
todo = []
for o, own in zip(outs, owners):
for c, (i, s) in zip(o.outputs, own):
raw = c.text.strip()
text = cap(raw, c.finish_reason == "stop") # cut off at max_tokens: drop the partial sentence
stats["capped"] = stats.get("capped", 0) + (text != raw)
v = violations(text)
stats["samples"] += 1
if v:
stats["rejected"] += 1
for r in v:
stats["reasons"][r] = stats["reasons"].get(r, 0) + 1
if best[i][s] is None or len(v) < best[i][s][0]:
best[i][s] = (len(v), text)
todo.append((i, s))
else:
good[i][s].append(text)
rows = []
for i in range(len(imgs)):
r = [None if (i, s) not in asked else good[i][s][0] if good[i][s] else best[i][s][1] for s in (0, 1)]
rows.append((r[0], r[1], all(good[i][s] for s in (0, 1) if (i, s) in asked)))
return rows
def fix(args):
"""Regenerate, in finished shards, only the captions that violate the current rules (one slot at a time).
Each shard's jsonl is rewritten atomically and marked ``.fixed``; workers claim shards like ``run``.
"""
out = Path(args.out)
llm, sp = engine(args)
pool = ThreadPoolExecutor(args.workers)
rank = os.environ.get("CUDA_VISIBLE_DEVICES", "0")
for shard in map(Path, args.shards):
stem = shard.stem
if not (out / f"{stem}.done").exists() or (out / f"{stem}.fixed").exists():
continue
try: # own lock name: ``claim`` skips shards that are already .done
os.close(os.open(out / f"{stem}.fixlock", os.O_CREAT | os.O_EXCL))
except FileExistsError:
continue
if (out / f"{stem}.fixed").exists(): # finished by another worker between the check and the claim
(out / f"{stem}.fixlock").unlink(missing_ok=True)
continue
rows = [json.loads(l) for l in open(out / f"{stem}.jsonl")]
bad = {r["key"]: [s for s in (0, 1) if violations(r[f"recap_{s + 1}"])] for r in rows}
bad = {k: v for k, v in bad.items() if v}
st = {"images": len(bad), "slots": sum(map(len, bad.values())), "samples": 0, "rejected": 0, "reasons": {},
"fallback": []}
items = [(k, j) for k, j, _ in read_shard(shard) if k in bad]
new, t0 = {}, time.time()
for c in range(0, len(items), args.chunk):
chunk = items[c : c + args.chunk]
imgs = list(pool.map(lambda x: load_image(x[1]), chunk))
todo = [(i, s) for i, (k, _) in enumerate(chunk) for s in bad[k]]
for (k, _), (r1, r2, ok) in zip(chunk, recaption(llm, sp, imgs, False, args.retries, st, todo)):
new[k] = (r1, r2)
if not ok:
st["fallback"].append(k)
tmp = out / f"{stem}.jsonl.tmp"
with open(tmp, "w") as f:
for r in rows:
for s, t in enumerate(new.get(r["key"], (None, None))):
if t is not None:
r[f"recap_{s + 1}"] = t
f.write(json.dumps(r) + "\n")
os.replace(tmp, out / f"{stem}.jsonl")
sj = out / f"{stem}.stats.json"
allst = json.load(open(sj))
allst["fix"] = st
json.dump(allst, open(sj, "w"))
(out / f"{stem}.fixed").touch()
(out / f"{stem}.fixlock").unlink(missing_ok=True)
print(f"[gpu{rank}] fixed {stem}: {st['slots']} captions of {st['images']} images in "
f"{time.time() - t0:.0f}s, still violating {len(st['fallback'])}", flush=True)
def _ngrams(t: str, n: int = 2) -> set:
w = re.findall(r"\w+", t.lower())
return {tuple(w[i : i + n]) for i in range(len(w) - n + 1)}
def _lcs(a: list, b: list) -> int:
prev = [0] * (len(b) + 1)
for x in a:
cur = [0]
for j, y in enumerate(b):
cur.append(prev[j] + 1 if x == y else max(prev[j + 1], cur[j]))
prev = cur
return prev[-1]
def similarity(a: str, b: str) -> dict:
"""Bigram Jaccard and ROUGE-L F1 between two captions."""
ga, gb = _ngrams(a), _ngrams(b)
wa, wb = re.findall(r"\w+", a.lower()), re.findall(r"\w+", b.lower())
l = _lcs(wa, wb)
return {"jaccard2": len(ga & gb) / max(1, len(ga | gb)), "rougeL": 2 * l / max(1, len(wa) + len(wb))}
def stats(args):
rows = [json.loads(l) for p in args.files for l in open(p)]
agg = {"images": 0, "samples": 0, "rejected": 0, "reasons": {}, "fallback": 0, "gen_s": 0.0, "wall_s": 0.0}
for p in args.files:
s = json.load(open(Path(p).with_suffix(".stats.json")))
for k in ("images", "samples", "rejected", "gen_s", "wall_s"):
agg[k] += s.get(k, 0)
agg["fallback"] += len(s["fallback"])
for r, c in s["reasons"].items():
agg["reasons"][r] = agg["reasons"].get(r, 0) + c
first = 2 * agg["images"] # first-pass samples
print(json.dumps(agg, indent=1))
print(f"img/s (generation only) {agg['images'] / agg['gen_s']:.2f}, (wall) {agg['images'] / agg['wall_s']:.2f}")
print(f"rejected / all samples {agg['rejected'] / agg['samples']:.3f}; resample overhead "
f"{agg['samples'] / first - 1:.3f}; images with a fallback caption {agg['fallback'] / agg['images']:.4f}")
for strict in (False, True):
final = [violations(r[k], strict=strict) for r in rows for k in ("recap_1", "recap_2")]
print(f"final captions still violating ({'extended' if strict else 'spec'} rules) "
f"{sum(map(bool, final)) / len(final):.4f}")
wc = sorted(len(r[k].split()) for r in rows for k in ("recap_1", "recap_2"))
print(f"words: p5 {wc[len(wc) // 20]} median {wc[len(wc) // 2]} p95 {wc[19 * len(wc) // 20]}")
rng = random.Random(0)
sub = rng.sample(rows, min(args.sim, len(rows)))
pair = [similarity(r["recap_1"], r["recap_2"]) for r in sub]
other = [similarity(r["recap_1"], rng.choice(rows)["recap_2"]) for r in sub] # different images: floor
orig = [similarity(r["recap_1"], r["orig_caption"]) for r in sub]
for name, s in (("recap_1 vs recap_2 (same image)", pair), ("recap_1 vs orig (same image)", orig),
("recap_1 vs recap_2 (random image)", other)):
print(f"{name}: " + ", ".join(f"{k} {sum(x[k] for x in s) / len(s):.3f}" for k in s[0]))
def export(args):
"""One parquet per shard (tar order, keys unique), row counts checked against the subset manifest."""
import pyarrow as pa
import pyarrow.parquet as pq
src, out = Path(args.src), Path(args.out)
out.mkdir(parents=True, exist_ok=True)
cols = ("key", "source_shard", "orig_caption", "recap_1", "recap_2")
total = 0
for sh in json.load(open(args.manifest))["shards"]:
stem = Path(sh["file"]).stem
assert (src / f"{stem}.done").exists(), f"{stem} not finished"
rows, seen = [], set()
for line in open(src / f"{stem}.jsonl"):
try:
r = json.loads(line)
except json.JSONDecodeError: # a line cut by a killed worker
continue
if r["key"] not in seen:
seen.add(r["key"])
rows.append(r)
assert len(rows) == sh["pairs"], f"{stem}: {len(rows)} rows, manifest {sh['pairs']}"
pq.write_table(pa.table({c: [r[c] for r in rows] for c in cols}), out / f"{stem}.parquet", compression="zstd")
total += len(rows)
print(f"{total} rows -> {out}")
if __name__ == "__main__":
ap = argparse.ArgumentParser()
sub = ap.add_subparsers(dest="cmd", required=True)
r = sub.add_parser("run")
r.add_argument("--shards", nargs="+", required=True)
r.add_argument("--out", required=True)
r.add_argument("--model", default=MODEL)
r.add_argument("--limit", type=int, default=0, help="images per shard (test runs; no .done marker)")
r.add_argument("--chunk", type=int, default=1024)
r.add_argument("--no-ban", action="store_true", help="no decode-time bans (filter + resample only)")
r.add_argument("--retries", type=int, default=3)
r.add_argument("--focus", action="store_true", help="add the FOCUS sentence to the second caption's prompt")
r.add_argument("--gpu-mem", type=float, default=0.85)
r.add_argument("--workers", type=int, default=16)
r.add_argument("--seed", type=int, default=0)
x = sub.add_parser("fix", help="regenerate only the captions that violate the current rules")
x.add_argument("--shards", nargs="+", required=True)
x.add_argument("--out", required=True)
x.add_argument("--model", default=MODEL)
x.add_argument("--chunk", type=int, default=1024)
x.add_argument("--retries", type=int, default=3)
x.add_argument("--gpu-mem", type=float, default=0.85)
x.add_argument("--workers", type=int, default=16)
x.add_argument("--seed", type=int, default=0)
x.add_argument("--no-ban", action="store_true")
s = sub.add_parser("stats")
s.add_argument("files", nargs="+")
s.add_argument("--sim", type=int, default=500)
e = sub.add_parser("export")
e.add_argument("--src", required=True)
e.add_argument("--out", required=True)
e.add_argument("--manifest", required=True)
a = ap.parse_args()
{"run": run, "fix": fix, "stats": stats, "export": export}[a.cmd](a)