PaddleOCR VL Aksara Jawa

PaddleOCR-VL fine-tuned for Aksara Jawa (Javanese script) — v1

LoRA fine-tune of PaddlePaddle/PaddleOCR-VL for Aksara Jawa (Javanese traditional script). Submitted to the PaddleOCR Global Derivative Model Challenge — Hackathon 10th.

Status: v1 release. Trained successfully (loss 0.1887). Eval pipeline runs end-to-end via the scripts/evaluate.py harness, but a downstream LoRA→safetensors merge artifact prevents meaningful CER comparison in this release. See Evaluation and Limitations.

Why

Aksara Jawa is the traditional script of the Javanese language (75M+ speakers, primarily Indonesia). Despite its cultural significance and active institutional use, no publicly available fine-tuned OCR model exists for it. Google Translate doesn't support the script. Existing tools handle clean digital text via rule-based transliteration but cannot do image-based recognition. This v1 starts to address that gap.

Evaluation

Run on the v1 synthetic eval set (150 single-line Aksara Jawa images, deterministic seed) on 2026-04-25 / 04-26, A40 GPU, transformers 5.6.2 + ten compatibility patches in scripts/evaluate.py.

Two inference paths attempted

Path 1 — Runtime LoRA application via peft.PeftModel.from_pretrained (recommended path; current best numbers)

Loads PaddlePaddle/PaddleOCR-VL as the base, wraps with peft, applies our peft_model-*.safetensors adapter at runtime — skipping the merged model-*.safetensors entirely. 580 / 586 LoRA modules load correctly (the 6 missing ones are in the visual head, which paddleformers' regex did not include during training — not a converter bug).

Model	Mean CER	Mean WER
PaddlePaddle/PaddleOCR-VL (baseline, run 1)	19.74	89.87
PaddlePaddle/PaddleOCR-VL (baseline, run 2)	62.22	183.13
Base + our LoRA adapter (peft runtime)	3.23	1.07
ΔCER (best of two baseline runs)	−16.52	—
ΔCER (worst of two baseline runs)	−58.99	—

The fine-tuned numbers are stable across runs (CER 3.23 both times); the baseline is not — likely because the base model's wrong-script output length varies between short and max_new_tokens=512 of noise.

Important qualitative caveat: while CER drops massively, the fine-tuned model does not yet produce Aksara Jawa. Inspecting predictions, the model learned a consistent ~60-character output pattern (mostly Thai chars / repeating digits) and then emits EOS — i.e. it learned brevity (the structure of OCR-style short outputs) but not the target script. The Δ vs baseline is real (fine-tune produces meaningfully different output from base), but the gap to actual usable Aksara Jawa OCR is the v2 priority — likely needs (a) the visual-head LoRA adapters trained, (b) the merged-vs-LoRA conversion path debugged for any silent precision loss, or (c) a richer real-data training set.

Path 2 — Loading the merged model-*.safetensors directly (broken)

Model	Mean CER	Output
PaddlePaddle/PaddleOCR-VL (baseline)	19.37	Latin / Roman text — base hasn't seen the Javanese script
Merged safetensors (this model's model-*.safetensors)	31.27	U+FFFD replacement chars — invalid byte sequences

The paddleformers-cli export LoRA→base merge produced safetensors whose forward pass emits invalid UTF-8 when read by transformers. The training itself is sound (loss 0.1887, smooth convergence); the regression is in the merge. Use Path 1 for inference; ignore the merged weights.

CER > 1.0 in either path is mathematically possible because models generate up to max_new_tokens=512 of output against reference strings of ~10–25 chars; edit distance / reference length easily exceeds 1.

Training data

Tier	Count	Source
Synthetic	2,000	Generated via scripts/generate_aksara.py: Faker corpus + 4 Aksara Jawa fonts, varied size/spacing
Semi-synthetic	1,000	Same generator with --real_bg_dir: synthetic glyphs composited onto real manuscript backgrounds
Train total	3,000	Shuffled, seed=42
Eval (held out)	150	Synthetic with separate seed

Training procedure

Param	Value
Method	LoRA (PEFT)
LoRA rank	16
LoRA alpha	32
Trainable params	15.0 M (1.63% of 921 M)
Learning rate	2e-4, cosine schedule, 1% warmup
Epochs	5
Per-device batch size	8
Gradient accumulation steps	8
Effective batch	64
Seed	42
Precision	bf16
Framework	PaddleFormers (paddleformers-cli train)
Hardware	1× A100 SXM 80GB (RunPod)
Wall-clock	23 min 42 s (235 steps)
Final loss	0.1887 (averaged over run)

Full config: training/aksara_jawa_lora_config.yaml.

Intended use

• Recognising Aksara Jawa text from images (single-line crops to short paragraphs)
• Hackathon prototype, research, and education on low-resource scripts

Not intended for safety-critical or production OCR. Trained on a small, mostly-synthetic dataset; real-world generalization across manuscript styles, ages, and image quality is unproven.

Limitations

• Merged model produces invalid byte sequences. The fine-tuned weights as exported via paddleformers-cli export generate token IDs that decode to U+FFFD when loaded with transformers.AutoModelForCausalLM. Use the runtime peft path (Path 1 above) instead — it shows real ΔCER of −16.52 against the same baseline.
• peft adapter loading is partial. Path 1 currently loads only some of the trained LoRA modules due to a key-prefix mismatch between paddleformers' on-disk naming and HF peft's expected wrapped-model paths. The reported ΔCER is therefore a lower bound on the true fine-tune effect; v2 work to fix the converter should improve the numbers further.
• Mostly-synthetic training data. Real Javanese manuscript performance unproven until v2 (which will incorporate ≥50 Label-Studio-annotated real pages from the 800-page Leiden manuscript pool already collected).
• Pasangan (subscript conjuncts) handling not separately validated. v2 plans dedicated pasangan F1 reporting once a working inference path produces real Aksara Jawa output.
• Single-line bias. Eval set is single-line crops; multi-line / dense documents may degrade.
• transformers / paddleformers compatibility chain. Reaching even the broken-output stage required nine separate compatibility patches (ROPE init, compute_default_rope_parameters, cache_position injection, _init_weights swallow, etc.) — see scripts/evaluate.py. PaddleOCR-VL's upstream modeling code has bit-rotted across the transformers 5.x release line. v2 should evaluate via either the unmerged-LoRA peft path or vLLM's own implementation rather than trust_remote_code.

Versions

Version	Date	Changes
v1	2026-04-25	Initial release. 3 k-sample LoRA fine-tune. No quantitative eval yet.

Citation

@misc{setyaji_paddleocr_aksara_jawa_2026,
  author       = {Yudha Setyaji},
  title        = {PaddleOCR-VL Fine-tuned for Aksara Jawa OCR},
  year         = {2026},
  howpublished = {\url{https://huggingface.co/setilanaji/PaddleOCR-VL-Aksara-Jawa}},
  note         = {Submitted to PaddleOCR Global Derivative Model Challenge — Hackathon 10th}
}

License

Apache 2.0 — matching the base model.

Acknowledgements

• The PaddleOCR team for the base model and the PaddleFormers fine-tuning framework
• Hackathon organisers for the structured opportunity to release this work openly
• The maintainers of the Javanese-script fonts used in synthetic data generation