Creates a grid with squares bisected into triangles. You can pass in an array of int to color certain sectors. It will save to a png

TriGridImage.java

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
public class TriGridImage {

	int cellsX,cellsY,resX,resY;
	VirtualTriangle[] sectors;
	
	public TriGridImage() {
		cellsY=6;
		cellsX=12;
		resX=resY=432;
		Init();
	}
	public TriGridImage(int cellsY, int resX, int resY) {
		this.cellsX=cellsY*2;
		this.cellsY=cellsY;
		this.resX=resX;
		this.resY=resY;
		Init();
	}
	private void Init() {
		sectors = new VirtualTriangle[this.cellsX*this.cellsY];
		for(int i=0;i<sectors.length;i++) {
			sectors[i]=new VirtualTriangle(i,resY/cellsY,this.cellsX);
		}
	}
	
	
	
	public void SetColor(int[] points) {
		SetColor(points, Color.magenta);
	}
	
	public void SetColor(int[] points, Color c) {
		if(points==null)
			return;

		if(c==null)
			c=Color.white;
		for(int i=0;i<points.length;i++) {
			sectors[points[i]-1].color=c;
		}
	}
	
	public void SaveToFile() {
		//you have chosen foolishly
		SaveToFile("GridOutput.png");
	}
	public void SaveToFile(String path) {
		BufferedImage img = new BufferedImage(resX,resY,BufferedImage.TYPE_INT_ARGB);
		Graphics2D graphics = img.createGraphics();
		for(int i=0;i<sectors.length;i++) {
			sectors[i].Draw(graphics);
		}
		try {
			ImageIO.write(img, "PNG", new File(path));
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public class VirtualTriangle{
		public Color color=Color.white;
		public int index,res,cellsPerRow;
		
		public VirtualTriangle(int index, int res,int cellsPerRow) {
			this.index=index;
			this.res=res;
			this.cellsPerRow=cellsPerRow;
		}
		public void Draw(Graphics g) {
			g.setColor(color);
			int[] xPoints = new int[3];
			int[] yPoints = new int[3];
			//starting row
			//Graphics coords start at top left, we need to start bottom left
			yPoints[0]=(cellsPerRow/2*res)-(index/cellsPerRow)*res;
			//starting column
			xPoints[0]=((index%cellsPerRow)/2)*res;
			int xText,yText;
			
			if(index%2!=0) {
				//even text numbers
				xPoints[1]=xPoints[0]+res;
				yPoints[1]=yPoints[0];
				xText=xPoints[0]+res/2;
				yText=yPoints[0]-res/4;
			}else {
				//odd text numbers
				xPoints[1]=xPoints[0];
				yPoints[1]=yPoints[0]-res;
				xText=xPoints[0]+res/4;
				yText=yPoints[0]-res/2;
			}
			xPoints[2]=xPoints[0]+res;
			yPoints[2]=yPoints[0]-res;
			g.fillPolygon(xPoints, yPoints, 3);
			g.setColor(Color.black);
			g.drawPolygon(xPoints,yPoints,3);
			//we start counting at 1 like a troglodyte
			String text =(index<9?"0":"")+(index+1);
			
			g.drawChars(text.toCharArray(), 0, text.length(), xText, yText);
		}
	}
	
}