OCR-Based Student Assessment System

🧠 Overview

The OCR-Based Student Assessment System automates the evaluation of handwritten exam scripts using Vision-Language Models (VLMs), Gemini-based assessment, and Retrieval-Augmented Generation (RAG).
It performs OCR, text evaluation, and figure analysis — providing a complete AI-based grading pipeline suitable for academic institutions.

---

🚀 Key Features

1. OCR Extraction (Text and Metadata)

• Uses Qwen2-VL-2B-Instruct, a vision-language model, to directly interpret handwritten text.
• Extracts student information (Name, ID, Course, etc.) from title pages.
• Detects question boundaries using standard markers such as:

  Answer to the question no-1a
  End of Answer-1a
  

2. Figure Segmentation and Evaluation

• Automatically detects and crops diagrams from scanned answer pages using OpenCV.
• Each extracted figure is evaluated using the Qwen2-VL and Gemini models.
• Outputs a structured JSON like:

  {
    "figure_number": "1a",
    "target": "heart",
    "caption": "Labeled diagram of human heart",
    "marks": 92
  }

3. Textual Assessment

• Evaluates student answers using semantic similarity and keyword matching.
• Combines three factors:
  • Semantic Similarity (SentenceTransformer embeddings)
  • Keyword Overlap (TF-IDF weighting)
  • Length Factor (relative completeness)
• Two scoring pipelines available:
  • Gemini 2.5 Flash (default) — API-based evaluation.
  • Prometheus RAG pipeline — local grading using textbook retrieval.

4. Batch Processing

• Accepts single or multi-student .zip archives.
• Automatically categorizes:
  • title → student info extraction
  • figure → figure segmentation + assessment
  • answer → full OCR + grading
• Merges all text into structured .txt files for downstream grading.

5. RAG Integration (Optional)

• Builds FAISS vector store from textbooks or PDFs for contextual grading.
• Enables Prometheus to access relevant content during evaluation.

6. Backend API (FastAPI)

• Provides RESTful endpoints for OCR, grading, and vector store management.
• Includes real-time streaming endpoints for batch script checking.
• Can run locally or deployed as a microservice.

---

⚙️ Architecture Summary

Component	Purpose
model_loader.py	Loads Qwen2-VL model (supports GPU and quantization).
ocr_engine.py	Extracts text and figures from scanned images.
figure_processor.py	Segments figures using OpenCV contour detection.
gemini_assessment.py	Grades answers with Gemini 2.5 Flash API.
gemini_figure_processor.py	Grades figures via Gemini multimodal reasoning.
assessment_core.py	Local semantic evaluation pipeline.
assessment_core_prometheus.py	RAG-enhanced Prometheus-based assessment.
rag_retriever.py	Retrieves semantically relevant content from FAISS index.
build_vector_store.py	Builds FAISS index from textbook PDFs.
semantic_chunking_vector_store.py	Alternative semantic chunking index builder.
batch_processor.py	Handles ZIP batch processing of multiple scripts.
database.py	Writes extracted student info and marks to CSV.
app.py	FastAPI backend server for API usage.
config.py	Stores configuration and prompt templates.

---

📂 Directory Structure

project_root/
├── app.py
├── batch_processor.py
├── ocr_engine.py
├── assessment_core.py
├── assessment_core_prometheus.py
├── gemini_assessment.py
├── gemini_figure_processor.py
├── figure_processor.py
├── model_loader.py
├── database.py
├── config.py
├── rag_retriever.py
├── semantic_chunking_vector_store.py
├── build_vector_store.py
├── format_answer.py
├── utils.py
├── main.py
├── output/
│   ├── text/
│   ├── figures/
│   └── assessments/
└── results/
    ├── students.csv
    └── marks.csv

---

🧩 Installation

Requirements

• Python 3.9 or higher
• CUDA GPU (optional but recommended)
• Minimum 8 GB VRAM (4 GB possible with quantization)

Setup

git clone <repo_url>
cd OCR-Based-Student-Assessment-System
python -m venv venv
source venv/bin/activate        # Linux/macOS
venv\Scripts\activate         # Windows
pip install -r requirements.txt

Check CUDA Availability

python cuda.py

---

🧠 Usage (CLI)

Single Student ZIP

python main.py /path/to/student_script.zip

Multi-Student Batch

python main.py --multi parent_batch.zip

Example ZIP Structure

parent_batch/
├── student_1/
│   ├── title.png
│   ├── figure_1.png
│   └── page_1.png
├── student_2/
│   ├── title.png
│   ├── figure_2.png
│   └── page_1.png

---

🖥️ Backend API (FastAPI)

Start Server

uvicorn app:app --host 0.0.0.0 --port 8000

Endpoints

1. Health Check

GET /health

Response:

{ "status": "ok" }

2. Upload PDF (Build Vector Store)

POST /api/v1/upload-pdf

Uploads a textbook PDF and rebuilds the FAISS index.

Response:

{ "status": "ok", "message": "Vector store rebuilt." }

3. Check Single Student Script

POST /api/v1/check-scripts

Accepts a .zip of scanned pages and rubric text, returns structured grading results.

4. Streamed Script Checking (Batch Mode)

POST /api/v1/batch-check-scripts-stream

Processes multi-student ZIP archives with real-time progress events.

---

📚 Vector Store Building

Create a semantic knowledge base from textbooks for context-aware evaluation:

python build_vector_store.py

or for advanced semantic chunking:

python semantic_chunking_vector_store.py

---

⚖️ Assessment Pipelines

Pipeline	Model	Description
Gemini (Default)	gemini-2.5-flash-lite	Fast API-based grading
Prometheus RAG	Local + FAISS	Contextual grading with textbook retrieval

---

⚠️ Limitations

• OCR accuracy varies with handwriting clarity.
• Prometheus pipeline requires GPU memory and FAISS index.
• Gemini API key required via .env.

---

👨‍💻 Authors

Developed by Tanjeeb Meheran Rohan and Afra Anika
Department of Computer Science and Engineering
Islamic University of Technology (IUT)

---

© 2025 — Academic and Research Use Only.