Halftone

This project is a Java Maven application built using NetBeans IDE and Swing that applies the effect of halftone to an image, with dots, lines or sine waves as the pattern. This code uses a codebase from my other project to separate the CMYK/RGB colors.

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Table of Contents

1. Features
2. Usage
3. How It Works
4. Additional Examples

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Features

• Apply Halftone Effect
  • Patterns: Dots, Polygons, Triangles, Stippling, Lines, Sine Waves.
• Full CMYK/RGB Processing
  • Separates image into CMYK/RGB channels, applies halftone at predetermined angles, and merges using multiply/screen blend.
• Drag & Drop Support
  • Simply drag images into the interface to process them.
• Interactive Controls
  • Adjust halftone scale (0–100) and angle (0°–360°) via sliders for live preview.
• Batch Processing
  • Drop multiple images at once; each will be processed and automatically saved.

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Usage

1. Open the Application

   • Double-click Halftone.jar, or run:

     java -jar Halftone.jar
     

2. Configure Settings

   • Pattern: Choose between Dots, Squares, Triangles, Lines or Sine Waves.
   • Scale Slider: Adjust the size of the halftone elements (0 = minimum, 100 = maximum).
   • Angle Slider: Define the angle of the halftone pattern (0°–360°).
   • Color Mode: Choose between Default, CMYK or RGB for color processing.

   

3. Drag & Drop

   • Drag one or more images (JPEG, PNG, JPG) directly into the window.

4. Preview and Save

   • A live preview will display the result.
   • To save, click Save or close the window. Processed images are saved in the same folder as the originals with this pattern:

     originalname_Halftone[type;scale;angle].png
     

   • Example: cameraman_Halftone[Lines;50;45.0].png

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How It Works

Below is a high-level overview of the halftone algorithm (example based on line/sine patterns):

1. Kernel Generation

   • Divide the image into square blocks (“kernels”), each rotated by the chosen angle.
   • For each kernel, sum up the RGB values and compute the average.

   

   To better understand the logic behind the kernels try out my kernel simulator!

2. Luminance Calculation

   • Within each kernel, convert the average color to luminance.
   • Determine a center point and compute two offset points based on luminance, constrained to half the kernel size.

   

3. Polygon Filling

   • Negative offsets define the top of a polygon, positive offsets define the bottom.
   • Connect these points along each row to create a complex shape that follows the image’s contours at the given angle.

   

4. CMYK/RGB Processing (Optional)

   • When CMYK/RGB mode is enabled, repeat steps 1–3 for each channel using fixed angles (e.g., CMYK(15°, 75°, 0°, 45°) or RGB(0º, 60º, 120º).
   • Finally, blend all channels using a multiply/screen operation to obtain the full-color halftone result.

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Additional Examples

Angles:

Wave crosshatching:

Stippling:

Overlaying halftones at opposing angles to create a cross-hatching effect, by adding some rotation and spacing error we can mimic a hand made pattern. This effect can be further enhanced by generating an outline (e.g., with Extended Difference of Gaussians).

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