ismatsamadov/handwriting-recognition-iam

Handwriting Recognition (CNN-BiLSTM-CTC)

A complete handwriting recognition system using a CNN-BiLSTM-CTC architecture trained on the IAM handwriting database. Achieves 12.95% CER and 42.47% WER on the IAM test set.

Hugging Face: IsmatS/handwriting_recognition

Quick Start

pip install torch torchvision pillow numpy huggingface_hub

import torch
import torch.nn as nn
import numpy as np
from PIL import Image
from huggingface_hub import hf_hub_download

# Download model checkpoint
ckpt_path = hf_hub_download(repo_id="IsmatS/handwriting-recognition-iam", filename="best_model.pth")
checkpoint = torch.load(ckpt_path, map_location="cpu")

# Character mapper from checkpoint
char_mapper = checkpoint['char_mapper']

def preprocess_image(image_path, target_height=64, target_width=256):
    img = Image.open(image_path).convert('L')  # grayscale
    img = img.resize((target_width, target_height), Image.LANCZOS)
    img = np.array(img, dtype=np.float32) / 255.0
    img = (img - 0.5) / 0.5  # normalize to [-1, 1]
    return torch.FloatTensor(img).unsqueeze(0).unsqueeze(0)  # (1, 1, H, W)

def ctc_decode(predictions, char_mapper):
    """Greedy CTC decoding."""
    pred_indices = predictions.argmax(dim=2).squeeze(1).tolist()
    decoded = []
    prev = None
    for idx in pred_indices:
        if idx != prev and idx != 0:  # 0 = blank token
            decoded.append(char_mapper.idx_to_char[idx])
        prev = idx
    return ''.join(decoded)

# Note: CRNN class must match the training definition in train_colab.ipynb
# See train_colab.ipynb for the full model class
# model = CRNN(num_chars=len(char_mapper.chars))
# model.load_state_dict(checkpoint['model_state_dict'])
# model.eval()
#
# img_tensor = preprocess_image("handwriting_sample.png")
# with torch.no_grad():
#     output = model(img_tensor)  # (T, 1, num_chars)
# text = ctc_decode(output, char_mapper)
# print("Recognized:", text)

Note: The trained model weights (best_model.pth) are generated during training. Run train_colab.ipynb on Google Colab to produce the checkpoint, then use the code above for inference.

📁 Files

1. analysis.ipynb - Dataset Analysis

• —Exploratory Data Analysis (EDA)
• —5 detailed charts saved to charts/ folder
• —Run locally or on Colab (no GPU needed)

2. train_colab.ipynb - Model Training (GPU)

• —⚡ Google Colab GPU compatible
• —Full training pipeline
• —CNN-BiLSTM-CTC model (~9.1M parameters)
• —Automatic model saving
• —Download trained model for deployment

🚀 Quick Start

Option 1: Analyze Dataset (Local/Colab)

jupyter notebook analysis.ipynb

• —No GPU needed
• —Generates 5 EDA charts
• —Fast (~2 minutes)

Option 2: Train Model (Google Colab GPU)

1. 1.Upload `train_colab.ipynb` to Google Colab
2. 2.Change runtime to GPU:
3. 3.Runtime → Change runtime type → GPU (T4 recommended)
4. 4.Run all cells
5. 5.Download trained model (last cell)

Training Time: ~1-2 hours for 20 epochs on T4 GPU

📊 Charts Generated

From analysis.ipynb:

1. 1.charts/01_sample_images.png - 10 sample handwritten texts
2. 2.charts/02_text_length_distribution.png - Text statistics
3. 3.charts/03_image_dimensions.png - Image analysis
4. 4.charts/04_character_frequency.png - Character distribution
5. 5.charts/05_summary_statistics.png - Summary table

🎯 Model Details

Architecture:

• —CNN: 7 convolutional blocks (feature extraction)
• —BiLSTM: 2 layers, 256 hidden units (sequence modeling)
• —CTC Loss: Alignment-free training

Dataset: Teklia/IAM-line (Hugging Face)

• —Train: 6,482 samples
• —Validation: 976 samples
• —Test: 2,915 samples

Metrics:

• —CER (Character Error Rate)
• —WER (Word Error Rate)

💾 Model Files

After training in Colab:

• —best_model.pth - Trained model weights
• —training_history.png - Loss/CER/WER plots
• —predictions.png - Sample predictions

📦 Requirements

torch>=2.0.0
datasets>=2.14.0
pillow>=9.5.0
numpy>=1.24.0
matplotlib>=3.7.0
seaborn>=0.13.0
jupyter>=1.0.0
jiwer>=3.0.0

🔧 Usage

Load Trained Model

import torch

# Load checkpoint
checkpoint = torch.load('best_model.pth')
char_mapper = checkpoint['char_mapper']

# Create model
from train_colab import CRNN  # Copy model class
model = CRNN(num_chars=len(char_mapper.chars))
model.load_state_dict(checkpoint['model_state_dict'])
model.eval()

# Predict
# ... (preprocessing + inference)

📝 Notes

• —GPU strongly recommended for training (use Colab T4)
• —Training on CPU will be extremely slow (~20x slower)
• —Colab free tier: 12-hour limit, sufficient for 20 epochs
• —Model checkpoint includes character mapper for deployment

🎓 Training Tips

1. 1.Start with fewer epochs (5-10) to test
2. 2.Monitor CER/WER - stop if not improving
3. 3.Increase epochs if still improving (up to 50)
4. 4.Save checkpoint before Colab disconnects
5. 5.Download model immediately after training

📄 License

Dataset: IAM Database (research use)