Image Manipulation using OpenCV - Assignment 2

📋 Overview

This project implements an image manipulation system using OpenCV and C++. It demonstrates fundamental image processing operations including contrast enhancement, rotation, and flipping using Object-Oriented Programming principles.

🎯 Features

• ✅ Load and display images
• ✅ Manual contrast enhancement (without convertTo())
• ✅ Adjustable brightness control
• ✅ Image rotation (90°, 180°, 270°)
• ✅ Image flipping (horizontal, vertical, both)
• ✅ Interactive menu-driven interface
• ✅ Save processed images
• ✅ Object-oriented design with proper encapsulation

📁 Project Structure

ImageManipulator/
├── ImageManipulator.h       # Header file with class declaration
├── ImageManipulator.cpp     # Implementation file
├── main.cpp                 # Main program with interactive menu
├── demo.cpp                 # Automated demonstration (optional)
├── CMakeLists.txt          # CMake build configuration
└── README.md               # This file

🔧 Prerequisites

Required Software:

1. C++ Compiler

   • GCC 7.0+ (Linux/Mac)
   • Visual Studio 2017+ (Windows)
   • Clang 5.0+

2. OpenCV Library (Version 3.x or 4.x)

   • Install on Ubuntu/Debian:

     sudo apt-get update
     sudo apt-get install libopencv-dev

   • Install on macOS:

     brew install opencv

   • Install on Windows: Download from OpenCV.org

3. CMake (Optional, version 3.10+)

   sudo apt-get install cmake  # Ubuntu/Debian
   brew install cmake          # macOS

🚀 Building the Project

Method 1: Using CMake (Recommended)

# Create build directory
mkdir build
cd build

# Generate build files
cmake ..

# Compile
make

# Run the program
./ImageManipulator

Method 2: Manual Compilation

Linux/Mac:

g++ -o ImageManipulator main.cpp ImageManipulator.cpp `pkg-config --cflags --libs opencv4`
./ImageManipulator

Windows (with OpenCV installed):

g++ -o ImageManipulator.exe main.cpp ImageManipulator.cpp -I"C:\opencv\include" -L"C:\opencv\lib" -lopencv_core -lopencv_imgcodecs -lopencv_highgui -lopencv_imgproc
ImageManipulator.exe

Method 3: Using Visual Studio (Windows)

1. Create new C++ project
2. Add all .cpp and .h files
3. Configure OpenCV:
   • Project Properties → C/C++ → Additional Include Directories → Add OpenCV include path
   • Project Properties → Linker → Additional Library Directories → Add OpenCV lib path
   • Project Properties → Linker → Input → Add required .lib files
4. Build and run

📖 Usage Guide

Running the Main Program

1. Start the program:

   ./ImageManipulator

2. Enter image path when prompted:

   Enter image path: /path/to/your/image.jpg
   

3. Choose operations from menu:

   ========== Image Manipulator Menu ==========
   1. Display Original Image
   2. Enhance Contrast
   3. Rotate Image (90°)
   4. Rotate Image (180°)
   5. Rotate Image (270°)
   6. Flip Horizontally
   7. Flip Vertically
   8. Flip Both Directions
   9. Save Processed Image
   10. Load New Image
   0. Exit
   

Example Operations

Contrast Enhancement:

Choose option 2
Enter alpha: 1.5    (increases contrast)
Enter beta: 20      (increases brightness)

Alpha Guidelines:

• alpha > 1.0: Increases contrast (e.g., 1.5, 2.0)
• alpha = 1.0: No contrast change
• alpha < 1.0: Decreases contrast (e.g., 0.5, 0.7)

Beta Guidelines:

• beta > 0: Increases brightness (e.g., 20, 50)
• beta = 0: No brightness change
• beta < 0: Decreases brightness (e.g., -20, -50)

Rotation:

Choose option 3, 4, or 5
- Option 3: Rotates 90° clockwise
- Option 4: Rotates 180°
- Option 5: Rotates 270° (90° counter-clockwise)

Flipping:

Choose option 6, 7, or 8
- Option 6: Horizontal flip (mirror left-right)
- Option 7: Vertical flip (mirror top-bottom)
- Option 8: Both directions (equivalent to 180° rotation)

Running the Demo Program (Optional)

Compile and run the automated demo:

g++ -o demo demo.cpp ImageManipulator.cpp `pkg-config --cflags --libs opencv4`
./demo

This will automatically demonstrate all operations with preset values.

🔍 Implementation Details

Class Design

The ImageManipulator class follows OOP principles:

Encapsulation:

• Private data members (originalImage, processedImage, imagePath)
• Public interface methods for all operations

Key Methods:

1. loadImage(path) - Loads image from file
2. enhanceContrast(alpha, beta) - Manual pixel-by-pixel contrast adjustment
3. rotateImage(angle) - Rotates image by 90°, 180°, or 270°
4. flipImage(flipCode) - Flips image horizontally, vertically, or both
5. displayOriginal() - Shows original image
6. displayProcessed() - Shows processed image
7. saveImage(path) - Saves processed image to file

Contrast Enhancement Algorithm

Important: We do NOT use convertTo() as required by the assignment.

Manual Implementation:

for (int row = 0; row < height; row++) {
    for (int col = 0; col < width; col++) {
        for (each channel in pixel) {
            new_value = alpha * old_value + beta
            new_value = clamp(new_value, 0, 255)
            output_pixel[channel] = new_value
        }
    }
}

Why Manual Implementation?

• Demonstrates understanding of image structure
• Shows pixel-level manipulation skills
• Allows custom processing logic
• Educational value in learning low-level operations

📊 Sample Results

Contrast Enhancement Examples:

Parameters	Effect
alpha=1.5, beta=0	Increased contrast, same brightness
alpha=1.0, beta=50	Same contrast, increased brightness
alpha=1.3, beta=20	Both increased
alpha=0.7, beta=-30	Both decreased (darker, less contrast)

Geometric Transformations:

Operation	Result
Rotate 90°	Portrait ↔ Landscape conversion
Rotate 180°	Upside down
Flip Horizontal	Mirror image (left becomes right)
Flip Vertical	Upside down mirror

🐛 Troubleshooting

Issue: "Could not load image"

Solution:

• Check if file path is correct
• Ensure image format is supported (JPG, PNG, BMP, etc.)
• Use absolute path if relative path fails

Issue: "OpenCV not found"

Solution:

# Verify OpenCV installation
pkg-config --modversion opencv4

# If not found, reinstall OpenCV
sudo apt-get install libopencv-dev

Issue: Compilation errors

Solution:

• Ensure C++11 or later standard
• Check OpenCV include paths
• Verify all library links

Issue: Images not displaying

Solution:

• Check if display server is running (Linux)
• Ensure GUI support in OpenCV build
• Try saving image instead of displaying

📝 Assignment Checklist

• Image loading and display
• Contrast enhancement with user input (alpha/beta)
• Manual implementation (NO convertTo())
• Rotation by 90°, 180°, 270°
• Flipping (horizontal, vertical, both)
• Object-oriented implementation
• Class diagram
• Documentation and report
• Screenshots of results
• Explanation of operations

🎓 Learning Outcomes

After completing this assignment, you will understand:

1. Image Representation

   • Images as 2D/3D matrices
   • Pixel value ranges (0-255)
   • Color channels (BGR in OpenCV)

2. Linear Transformations

   • Contrast adjustment using multiplication
   • Brightness adjustment using addition
   • Clamping values to valid range

3. Geometric Transformations

   • Rotation mechanics
   • Flipping operations
   • Coordinate transformations

4. OOP in C++

   • Class design and encapsulation
   • Constructor/destructor usage
   • Method organization

5. OpenCV Basics

   • cv::Mat class
   • Image I/O operations
   • Basic image processing functions

📚 Additional Resources

• OpenCV Documentation
• OpenCV Tutorials
• Image Processing Fundamentals
• Linear Transformation in Images

🤝 Contributing

This is an academic assignment. If you want to extend it:

• Add more image filters (blur, sharpen, edge detection)
• Implement custom rotation angles
• Add histogram equalization
• Support batch processing

📄 License

This project is for educational purposes as part of an academic assignment.

✍️ Author

Jawad Ahmed
Roll Number: 533047 Course: Object Oriented Programming Assignment: Assignment 2 - Image Manipulation using OpenCV

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🎯 Quick Start Summary

# 1. Install OpenCV
sudo apt-get install libopencv-dev

# 2. Clone/Download project files

# 3. Build
mkdir build && cd build
cmake ..
make

# 4. Run
./ImageManipulator

# 5. Enter image path and enjoy!

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Last Updated: October 2025