Sticker Pack Generator

Sticker Pack Generator

End-to-end pipeline for Telegram sticker assets — covers all three pack types, both for hand-drawn PNG sequences from an artist and for AI-generated frames. Battle-tested on <your_pack_short_name>-style static, animated, and custom emoji packs for <YOUR_CHANNEL>.

When to use

• "Make me a sticker pack from this MP4 / PNG sequence"
• "Make a custom emoji pack for my channel reactions"
• "I have 75 PNG frames from an artist, turn them into an animated WebM pack"
• "Why does my hand-authored Lottie not fit 64KB"
• "VP9 with alpha — ffmpeg silently strips the alpha"
• "Set up the channel /setreactions with my custom emojis mixed with standard ones"

Three Telegram sticker formats (unified spec)

Source material: PNG sequence from artist

Default expected input: a numbered PNG sequence on disk.

<HOME>/sticker-pack/<character>/png_seq/0001.png
<HOME>/sticker-pack/<character>/png_seq/0002.png
...
<HOME>/sticker-pack/<character>/png_seq/NNNN.png

The sequence can come from any of these:

• An illustrator handing over baked frames (preferred — alpha is usually clean already).
• An MP4 from After Effects / Procreate Dreams — extract with ffmpeg:

  ffmpeg -i input.mp4 -vf "fps=30,crop=ih:ih,scale=512:512" "<HOME>/sticker-pack/<character>/png_seq/%04d.png"
  

• A gpt-image-2 generation (gpt-image-2-2026-04-21, /v1/images/generations). Note: background:"transparent" returns HTTP 400 — generate on cream/white, mask later.

Pipeline overview

PNG seq (alpha or RGB)
       │
       ├─► (if no alpha) SAM2 + rembg UNION mask  ──┐
       │                                            ▼
       │                                   per-frame chromakey
       │                                            ▼
       │                                   morph close + re-threshold
       │                                            ▼
       │                                   RGBA PNG frames
       │
       ▼
ffmpeg yuva420p raw stream  →  Google `alpha_encoder` (VP9 + BlockAdditional)
       │
       ▼
512×512 .webm  ──►  Telethon /newvideopack | /addsticker | /replacesticker
                                │
                                ▼
                  100×100 .webm  ──►  /newemojipack    (Custom Emoji)
                                │
                                ▼
                   document_id  ──►  MessageEntityCustomEmoji
                                          (UTF-16 offsets in caption)
                                │
                                ▼
                          /setreactions in channel admin

Step 1 — Mask extraction (SAM2 + rembg UNION + chromakey)

White-on-white characters break both rembg and SAM2 individually.

• rembg per-frame: flickers and drills holes through motion-blur frames.
• SAM2 single-click on a white body: only grabs the colored details, drops the body.

Solution = UNION of three sources:

# pseudo-code, full impl in scripts/process_png_seq.py
seed_mask = rembg(frame_0) | chromakey(frame_0, white_threshold=215)
masks = SAM2.add_new_mask(seed_mask).propagate_in_video(frames)
for i, frame in enumerate(frames):
    alpha = masks[i] | chromakey(frame, white_threshold=215)
    alpha = morph_close(alpha, kernel=5)
    alpha = rethreshold(alpha, lo=60, hi=180)   # kills trailing halo
    save_rgba(frame, alpha, f"rgba/{i:04}.png")

Notes:

• Chromakey threshold 235 leaves white halo; use 215.
• Morph close + re-threshold (under 60 → 0, over 180 → 255) cleans the SAM2 fuzzy edge.
• Flying props (mic, spatula) get lost by SAM2 — the per-frame chromakey UNION recovers them.

Step 2 — Frame-level alpha encoding (libvpx alpha_encoder, custom build)

ffmpeg -c:v libvpx-vp9 -pix_fmt yuva420p silently strips alpha when muxing to WebM. Every libvpx build through ffmpeg does this. The ONLY working path is Google's webm-tools/alpha_encoder which muxes alpha through Matroska BlockAdditional.

• It is Linux-only — run through WSL.
• The upstream master branch breaks at low CBR (50 kbps); the well-known patch to alpha_encoder.cc restores CBR + --target-bitrate=50.
• Battle-tested config: --end-usage=cbr --target-bitrate=50 --fps=30/1 --width=512 --height=512.
• Output: ~70–90 KB for a 3-sec sticker.

Build path (one-time):

git clone <webm-tools-fork-with-patch> ~/webm-tools
cd ~/webm-tools/alpha_encoder && make
# binary: ~/webm-tools/alpha_encoder/alpha_encoder

Step 3 — Compose into WebM (ffmpeg yuva420p stream → alpha_encoder)

ffmpeg -y -framerate 30 -i rgba/%04d.png \
  -pix_fmt yuva420p -f rawvideo - \
  | wsl ~/webm-tools/alpha_encoder/alpha_encoder \
       --width=512 --height=512 --fps=30/1 \
       --end-usage=cbr --target-bitrate=50 \
       -o out.webm

Verify in ffprobe: stream pix_fmt=yuva420p AND a sibling BlockAdditional track.

Step 4 — Custom emoji crop (100×100)

Telegram renders custom emoji inline at ~32×32. Source 512×512 → naive scale=100:100 makes characters unreadable. Two tradeoffs:

1. Tight bbox crop — find non-transparent bbox per frame, crop to it, then resize to 100×100. Maximises character visibility, but if motion is wide, you get bouncy framing.
2. Slight margin (10–15%) — crop bbox + margin from the union of bboxes across the entire clip. Stable framing, slightly smaller character.

Empirical: option 2 (union bbox + margin) wins for full-body characters; option 1 wins for head-only emojis.

Outline of ≥3px on key features (eyes, mouth, glasses) is mandatory or they disappear at 32×32.

Step 5 — Upload to Telegram (Telethon: NewStickerPack / AddSticker)

All upload scripts use Telethon, share scripts/_telethon_base.py, and key off ~/.claude/.credentials.master.env (TELEGRAM_API_ID, TELEGRAM_API_HASH). Session file: ~/.claude/telegram_session.

Pack short_name convention: <base>_by_<your_bot>. For emoji packs: <base>_emoji_by_<your_bot>.

All upload scripts map stickers by emoji, not by position — Telegram resorts video packs by upload date. Emojis must be VS16-normalised before comparing:

norm = lambda e: e.replace('️', '')

Step 6 — Custom emoji posting via MessageEntityCustomEmoji (UTF-16 offsets)

After a custom emoji is in a pack, every emoji becomes a document_id you can substitute for the literal Unicode emoji in any message you send via your user account (or any premium account; standard accounts only see them in channels where they're set as reactions).

from telethon.tl.types import MessageEntityCustomEmoji

text = "🔥 fire takes 🤝 hands"
# offsets are UTF-16 code units, not bytes, not chars
def utf16_len(s): return len(s.encode('utf-16-le')) // 2

entities = []
cursor = 0
for ch, doc_id in replacements:   # [(emoji_unicode, document_id), ...]
    idx = text.find(ch, cursor)
    off = utf16_len(text[:idx])
    length = utf16_len(ch)
    entities.append(MessageEntityCustomEmoji(off, length, document_id=doc_id))
    cursor = idx + len(ch)

await client.send_message(target, text, formatting_entities=entities)

formatting_entities= and parse_mode= are mutually exclusive — pick one. For mixed (HTML + custom emoji) build the entities list manually from client.parse_mode.parse(...) and append MessageEntityCustomEmoji entries.

Step 7 — Channel reactions setup (/setreactions admin panel)

A channel can have a mix of standard emoji reactions and custom ones. Both groups count toward Telegram's per-channel reaction cap.

Reference setup that works well on a tech channel:

• 73 standard emoji + 8 custom from the channel's own emoji pack.
• Custom picks pulled from the pack (🔥 ❤️ 🤔 🤯 🎉 🤝 🤩 🤣 — overwrite with your own).
• Daily story limit is gated by channel boost level (level N → ~N stories/day; level 8 → 8). Hitting the cap returns RPCError 400: BOOSTS_REQUIRED from SendStory. Deleting a sent story does NOT refund the daily slot.

Reactions are configured once via the @BotFather-less admin UI (channel → Edit → Reactions → All / Some). Скрипта-обёртки в паке нет; если нужна автоматизация — это один вызов Telethon EditChannelReactionsRequest (база подключения — scripts/_telethon_base.py).

TGS Lottie dead ends — DO NOT RETRY

This is the most expensive lesson in this skill. The painterly maximalist illustration style does NOT survive vectorisation under the 64KB TGS cap.

1. VTracer (Rust raster→SVG) — all 3 presets fail. default, binarized, cartoon, polygon — every output is "unwatchable" (user verdict). Cancelled.
2. Hand-authored SVG ($500–2000 studio quote). Doesn't capture painterly stylistic depth either — gradients-rich illustrations with 14 layered groups need too many vertices.
3. Per-frame animation as Lottie. 18 frames × ~21 KB per SVG path-set = ~382 KB raw, vs. 64 KB TGS hard cap. No amount of gzip closes that gap.
4. python-lottie raster→TGS toolchain. Depends on glaxnimate.dll — Windows build is Python 3.8 only. No path on Python 3.13.

Final negative finding: painterly raster character cannot fit the Telegram TGS hard cap. Stick to video WebM for emoji and stickers. The "TGS Lottie renders jumbo at large size like basketball 🏀" trick does not apply to character-based emoji at all.

Keep the bookkeeping packs (<name>_vector_test, <name>_static_test) around as evidence so you don't re-run this in three months.

Gotchas (9 items)

1. TGS 64KB cap — painterly = no go. Use video WebM (see dead-ends section).
2. SAM2 loses edges + rembg drifts on shadows → always UNION mask, morph close + re-threshold; threshold 235 leaves halo, use 215.
3. gpt-image-2 background:"transparent" → HTTP 400. Generate on cream/white, mask afterwards via SAM2+rembg UNION.
4. libvpx master breaks CBR 50kbps when building alpha_encoder — apply the well-known patch to alpha_encoder.cc.
5. Telethon 1.39 entity parsing: <spoiler>, <tg-spoiler>, ||x||, expandable blockquote are NOT parsed by html_parse. Build them manually: MessageEntitySpoiler(offset, length) and MessageEntityBlockquote(offset, length, collapsed=True) with UTF-16 offsets.
6. Custom emoji renders 32×32 inline in chat. Outline ≥3px on key features (eyes, mouth, glasses, badge), or they vanish.
7. Channel boost level caps daily story limit (lvl 8 → 8/day). 9th story returns RPCError 400: BOOSTS_REQUIRED. Deleting a story in the same day does NOT refund the slot. To fix bad stories without spending quota, use EditStoryRequest to swap media.
8. Workflow strict schema parameter crashes StructuredOutput parsers across all subagents — rerun without schema= and parse plain text.
9. Progress files *_done.txt block retries — rm -f before any rerun, or the script silently skips work.

Bonus:

• No parallel Telethon processes on the same .session — SQLite lock; copy the session file (shutil.copy) and override SESSION= env var for each worker.
• tg_client.py has NO send-album — older docs sometimes claim it does.
• @Stickers FloodWaitError after ~37 fast replaces; catch and await asyncio.sleep(fw.seconds + 5).
• Mapping by position is wrong — Telegram resorts video packs by upload date. Always key off emoji (VS16-normalised).
• pipe | tail on a long-running encode can SIGPIPE-kill the producer when the tail buffer fills. Pipe to a file instead.

Scripts catalogue

scripts/
├── _config.py                  — loads creds from ~/.claude/.credentials.master.env
├── _telethon_base.py           — shared Telethon client init
├── cuda_init.py                — CUDA DLL bootstrap (must import BEFORE sam2/rembg/torch)
│
├── process_png_seq.py          — PNG seq → SAM2+rembg UNION → yuva420p → alpha_encoder
├── batch_process.py            — batch wrapper around process_png_seq for a dir of seqs
├── make_emoji_variant.py       — 512px webm → 100×100 ≤256KB (union bbox + margin)
│
├── gen_mascot_reference.py     — gpt-image-2 master frame
├── gen_emotion.py              — single emotion via images/edits
├── batch_gen_emotions.py       — batch generate 75 emotion frames
├── tight_crop_alpha.py         — rembg cut + tight crop to 512 webp (for static pack)
│
├── upload_static_pack.py       — /newpack flow
├── create_pack.py              — /newvideopack flow
├── create_emoji_pack.py        — /newemojipack flow
├── add_to_pack.py              — /addsticker, skips already-present emojis
├── replace_in_pack.py          — /replacesticker, preserves slot, keyed by emoji
├── replace_all_custom_emojis.py — bulk text replace via MessageEntityCustomEmoji
├── clean_pack.py               — /delsticker (extras / duplicates)
├── check_pack.py               — GetStickerSet, dump current state
└── set_channel_reactions.py    — EditChannelReactionsRequest (mix standard + custom)

References

• references/png-seq-source.md — expected PNG-seq layout + how to extract from MP4 / gpt-image-2.
• references/static-vs-video-vs-emoji-spec.md — three formats unified spec (sizes, caps, render UX).
• references/sam2-rembg-pipeline.md — UNION mask details, threshold tuning, chromakey for flying props.
• references/vp9-alpha-encoder-setup.md — building alpha_encoder, the libvpx patch, CBR config.
• references/tgs-lottie-deadends.md — why painterly doesn't vectorise; the 64KB math; VTracer presets verdict.
• references/channel-reactions-setup.md — /setreactions workflow, boost-level story caps.
• references/custom-emoji-posting.md — MessageEntityCustomEmoji flow + UTF-16 offset helper.
• references/telegram-bot-flows.md — every @Stickers command flow as a state diagram.
• references/troubleshooting.md — failure-mode → diagnosis → fix.
• references/static-character-design.md — consistency strategy for 75 emotions on one mascot.
• references/sample-mascot-prompt.txt — reusable mascot prompt template.
• references/sample-emotions.json — 75-emotion list with constraint blocks.
• references/sample-mapping.json — sticker→emoji mapping example.

Triggers

• ru: "стикерпак", "видео-эмодзи", "альбом для канала", "кастом эмодзи", "VP9 alpha", "SAM2 mask", "пак для @-канала", "залей в Telegram", "transparent webm", "пак из mp4", "PNG-секвенция от художника", "TGS не лезет в 64KB"
• en: "sticker pack", "custom emoji", "vp9 alpha encoder", "telegram pack pipeline", "alpha_encoder cbr", "BlockAdditional alpha", "sam2 union mask", "rembg+sam2", "tgs lottie 64kb fail"

GitHub depersonalization checklist (when packaging for public)

When publishing this skill or its scripts as a standalone repo:

SCRUB:

• All @-handles → replace with <your_pack_short_name>, <your_channel>, <your_bot>.
• Real names of channels, packs, persons, products.
• Absolute paths containing user names: C:/Users/<user>/... → <HOME>/....
• API keys, tokens, channel IDs, TELEGRAM_API_ID, TELEGRAM_API_HASH.
• Session files (*.session, *.session-journal).
• Sample .env only as .env.example with placeholder values.
• Channel and pack screenshots — blur any identifying handles before checking in.

KEEP (this is the gold for other users):

• The technique: SAM2+rembg UNION, chromakey threshold 215, morph close + re-threshold.
• The libvpx alpha_encoder patch + CBR config.
• The TGS Lottie dead-end writeup — so nobody else wastes a week on it.
• UTF-16 offset helper for MessageEntityCustomEmoji.
• Boost-level story cap notes.
• All 9 gotchas as a top-of-README "DO NOT REDO" block.

PLACEHOLDERS to use consistently:

• <your_pack_short_name> — e.g. mymascot_by_examplebot
• <YOUR_CHANNEL> — e.g. @example_channel
• <HOME> — user home directory
• <TELEGRAM_API_ID>, <TELEGRAM_API_HASH> — credential placeholders
• <your_bot> — the bot suffix all packs must end with
• <character> — sticker-pack subject name