Platrix / README.md

Add unified CRNN whole-plate reader (segmentation-free) + update card

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license: mit
library_name: onnx
pipeline_tag: image-classification
tags:
  - ocr
  - persian
  - farsi
  - alpr
  - anpr
  - license-plate
  - iran
  - onnx
  - computer-vision
language:
  - fa

Persian ALPR Models — Iranian License Plates (ONNX)

A complete, portable model bundle for reading Iranian vehicle license plates, powering the Platrix real‑time ALPR engine. Every model ships as a portable ONNX graph, so it runs anywhere ONNX Runtime runs — no TensorFlow or PyTorch required at inference time.

The recommended pipeline is two models: detect the plate (YOLO) → read the whole plate (CRNN).

Author: Dibachain

Project & source code: https://github.com/AliAkrami1375/Platrix

Files

File	Description
`plate_yolo.onnx`	Plate detector — a YOLOv8 model that localizes the plate in a full frame (single "plate" class).
`ocr_crnn.onnx`	Whole‑plate reader (recommended) — a CRNN+CTC model that reads the entire plate in one pass (no character segmentation). Input `1×1×32×128` grayscale; output `(T, 33)` logits, CTC‑decoded. Trained on realistic full‑plate images with the official plate font + augmentation.
`ocr_crnn.labels.json`	Class list for the CRNN (CTC blank is the last index).
`ocr_cnn.onnx`	Per‑character classifier (alternative) — a small CNN that classifies a single segmented glyph (`1×1×32×32` → 28 classes). Trained on real plate character crops.
`ocr_cnn.labels.json`	Class list for the per‑character CNN.

How the pipeline works

Detect the plate in the frame with plate_yolo.onnx.
Read the whole plate crop with ocr_crnn.onnx (CRNN + CTC) — no character segmentation, so there are no split/merge errors. Output is decoded with a greedy CTC pass into the plate string.

The CRNN is trained on realistic full‑plate images rendered with the official Iranian plate font and layout, plus perspective / rotation / motion‑blur / illumination augmentation, so it transfers to real plate crops.

Usage — whole‑plate reader (recommended)

import json
import numpy as np
import cv2
import onnxruntime as ort
from huggingface_hub import hf_hub_download

onnx = hf_hub_download("Dibachain/ocr-persian", "ocr_crnn.onnx")
labels = json.load(open(hf_hub_download("Dibachain/ocr-persian", "ocr_crnn.labels.json"), encoding="utf-8"))
blank = len(labels)  # CTC blank is the last index

sess = ort.InferenceSession(onnx, providers=["CPUExecutionProvider"])
name = sess.get_inputs()[0].name

def read_plate(plate_bgr):
    gray = cv2.cvtColor(plate_bgr, cv2.COLOR_BGR2GRAY)
    img = cv2.resize(gray, (128, 32)).astype("float32") / 255.0
    logits = sess.run(None, {name: img.reshape(1, 1, 32, 128)})[0][0]  # (T, C)
    idx = logits.argmax(1)
    out, prev = [], -1
    for i in idx:
        if i != blank and i != prev and i < len(labels):
            out.append(labels[int(i)])
        prev = int(i)
    return "".join(out)      # e.g. "81و63813"

With Platrix (end‑to‑end)

git clone https://github.com/AliAkrami1375/Platrix.git
cd Platrix && pip install -r requirements.txt
huggingface-cli download Dibachain/ocr-persian \
    ocr_crnn.onnx ocr_crnn.labels.json plate_yolo.onnx --local-dir models/
platrix serve      # auto-uses YOLO + CRNN, dashboard on http://localhost:8080

Labels

CRNN (ocr_crnn.labels.json): the digits 0–9 and Persian plate letters (ا ب پ ت ث ج ح د ز ژ س ص ط ع ق ل م ن و ه ی). The CTC blank is the extra, last index (len(labels)).
Per‑character CNN (ocr_cnn.labels.json): 28 classes, one neuron per glyph.

Model architectures

CRNN reader: a 5‑block CNN → 2‑layer bidirectional LSTM → linear, trained with CTC loss. Input 1×1×32×128. ~96% exact‑plate accuracy on held‑out synthetic plates and strong transfer to real photos.
Per‑character CNN: Conv → Conv → Pool → Conv → Pool → FC → FC, trained on real plate character crops (~98% validation accuracy).

Intended use & limitations

Intended for parking, access control and traffic‑analytics pipelines that first detect and segment plates, then classify each character with this model.
Not an end‑to‑end plate reader on its own — it classifies single, pre‑segmented characters. Overall accuracy on a full plate depends on the quality of the upstream detection and segmentation.
Real‑world plates vary in font, angle, lighting and wear; for best results, pair with a strong plate detector and clean segmentation.