Turn images into life files

Lifinator.java

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import javax.imageio.ImageIO;

public class Lifeinator
{
  public static void main(String[] args)
  {
    try {
      File f = new File(args[0]);
      File o = new File("output.life");
      
      BufferedImage bi = ImageIO.read(f);
      FileWriter w = new FileWriter(o);
      
      for (int i = 0; i < bi.getHeight(); i++) {
        for (int j = 0; j < bi.getWidth(); j++) {
          Color c = new Color(bi.getRGB(j, i));
          int ca = (c.getRed() + c.getGreen() + c.getBlue()) / 3;
          if (ca < 127) {
            w.append("*");
          }
          else {
            w.append("-");
          }
        }
        w.append("\n");
      }
      
      w.close();
      System.out.println("done");
    }
    catch (IOException e) {
      e.printStackTrace();
    }
  } 
}