👁️ Java Face Detector — Mini Project

A simple but powerful Java project that performs face detection using OpenCV. The program scans an image, detects human faces using a pretrained Haar Cascade model, and highlights them using rectangles.

---

🧠 Tech Stack

Java • openCV • GitHub •ideaL

---

📸 Project Overview

This project demonstrates:

• Reading images in Java using OpenCV
• Detecting faces using Haar Cascade Model (haarcascade_frontalface_default.xml)
• Drawing rectangles around detected faces
• Saving the output image with detected faces

💡 Perfect beginner project for learning Java + Computer Vision.

---

📂 Project Structure

FaceDetectionProject/
├── lib/
│   └── opencv_java4120.dll              # Native library (NOT pushed to GitHub)
├── src/
│   ├── resources/
│   │   └── haarcascade_frontalface_default.xml
│   └── FaceDetector.java                # Main program
├── face.jpg                             # Input image
└── README.md

⚠ Note: Large OpenCV binaries (.dll, .jar) should NOT be pushed to GitHub. Instead, users must download them manually.

---

⚙️ Setup Instructions

1️⃣ Install OpenCV

Download the latest release from: 🔗 https://opencv.org/releases/

Find these files inside the extracted folder:

• opencv-4120.jar
• opencv_java4120.dll

---

2️⃣ Add Dependencies to Your Project

• Add opencv-4120.jar to your Build Path
• Add the folder containing the .dll to:

-Djava.library.path=lib

---

3️⃣ Add Haar Cascade File

Place inside:

src/resources/haarcascade_frontalface_default.xml

---

4️⃣ Add Input Image

Place any image as:

face.jpg

(or change the filename inside the code)

---

5️⃣ Compile & Run

javac -cp ".;lib/opencv-4120.jar" src/FaceDetector.java
java -cp ".;lib/opencv-4120.jar" -Djava.library_path=lib FaceDetector

---

6️⃣ Output

A new face.jpg file is generated with rectangles drawn around the detected faces.

---

💡 What I Learned

✔ Integrating OpenCV with Java ✔ Understanding Haar Cascade classifier ✔ Reading & writing images using OpenCV (Mat, Imgcodecs) ✔ Drawing on images (Imgproc.rectangle()) ✔ Handling native OpenCV libraries (.dll) ✔ Debugging vision errors (empty Mat, wrong path, detection issues) ✔ Organizing Java projects with external resources ✔ Using Git/GitHub with large-file exclusions

---

⚠ Important Notes

• Accuracy depends on lighting, face size, and angle
• Haar cascade should be the official OpenCV XML
• .dll / .exe files must NOT be pushed to GitHub
• Use a .gitignore for binaries

Example:

*.dll
*.exe
*.jar