How to create a .jar Processing app that you can launch from the command line

Generator.java

import processing.core.*;

public class Generator {
	
    private PApplet applet = null;
    private PGraphics context = null;
    
    
    Generator()
    {
    }
    
    
    void initialize(int _width, int _height)
    {
        applet = new PApplet();        
        context = applet.createGraphics(_width, _height, PApplet.P2D);
        applet.g = context;
    }

    void render(String _filename)
    {
        if (applet == null || context == null)
        {
            System.out.println("error: GraphRenderer::render(): call initialize() before rendering.");
            return;
        }
       
        context.beginDraw();
        context.background(0);
        context.fill(255);
        context.rect(0, 0, 200, 200);
        context.endDraw();
	
        context.save(_filename);
        
    }
}

jar.asciidoc

Create a Java project in Eclipse

When created, import Processings core.jar: http://processing.org/learning/eclipse/

In you Java Project, create the attached files.

To export as a .jar file, right-click your project. Choose "Java > runnable Jar". Remember to choose you MainClass as the main class in the dialog.

give you .jar file a name. Press export.

Now run your .jar file on the command line using: java -jar MyJarName.jar

MainClass.java

public class MainClass {
	
	public static void main(String args[])
    {	
		Generator g = new Generator();
        g.initialize(400, 400);
        g.render("test.png");	
    }    
}