📷 Image Enhancement Algorithms in Java

This project demonstrates two fundamental image enhancement algorithms implemented using Java and Polymorphism:

• Contrast Stretching
• Histogram Equalization

These techniques aim to improve the visual quality of grayscale images by modifying pixel intensity distributions.

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🔧 How It Works

We use a shared interface:

public interface ImageProcessor {
    BufferedImage process(BufferedImage input);
}

Each algorithm implements this interface and processes a grayscale image accordingly.

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🧪 Algorithms

1. Contrast Stretching

This method increases the dynamic range of pixel intensities by stretching them linearly across the full range [0, 255].

• Formula:

new_pixel = (pixel - min) * 255 / (max - min)

• Improves contrast when image pixels are clustered in a narrow intensity range.

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2. Histogram Equalization

This method redistributes pixel intensities to produce a more uniform histogram (i.e., balanced contrast across the image).

• Steps:

  1. Calculate histogram.

  2. Compute CDF (Cumulative Distribution Function).

  3. Normalize using:

     new_pixel = round((CDF(pixel) - CDF_min) / (total_pixels - CDF_min) * 255)
     

• Useful when the image has uneven brightness or lacks detail.

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⚖️ Comparison Table

Feature	Contrast Stretching	Histogram Equalization
🔍 Goal	Expand contrast range	Redistribute intensity levels
🧮 Formula	Linear mapping based on min & max	Non-linear mapping using CDF
🟢 Best For	Images with poor contrast	Images with uneven intensity/brightness
⚙️ Complexity	Simple (linear)	Moderate (requires histogram + CDF)
💡 Output Style	Preserves structure with more contrast	Enhances global contrast
🎯 Risk of Over-enhancement	Low	Moderate (can cause over-saturation)

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🚀 Usage

1. Add your image to the root directory as input.jpg.

2. Choose algorithm:

ImageProcessor processor = new ContrastStretchingProcessor(); 
// OR
ImageProcessor processor = new HistogramEqualizationProcessor();

3. Run the program:

java Main

4. Output saved as output.jpg.

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📂 Project Structure

src/
│
├── Main.java
├── ImageProcessor.java
├── ContrastStretchingProcessor.java
├── HistogramEqualizationProcessor.java
├── ImageProcessingAPI.java

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🧠 Future Work

• GUI interface using JavaFX/Swing.
• Color image support.
• Web API using Spring Boot.

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