import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;


public class Threshold {

public static BufferedImage threshold (BufferedImage input, int level)
{
    int img_height = input.getHeight();
    int img_width = input.getWidth();
    BufferedImage output_img = new BufferedImage (img_width, img_height, BufferedImage.TYPE_INT_RGB);


    for (int x = 0; x < img_width; x++)
    {
        for (int y = 0; y < img_height; y++)
        {
            int r = getRedValue(input, x, y);
            int g = getGreenValue(input, x, y);
            int b = getBlueValue(input, x, y);

            int average = (r + g + b) / 3;

            if (average < level) {
                average = 0;
            } else if (average > level) {
                average = 255;
            }

            Color average_color = new Color(average, average, average);
            output_img.setRGB(x, y, average_color.getRGB());
        }
    }
    return output_img;
}
}

public static int getRedValue(BufferedImage img, int x, int y) {
    Color col = new Color(img.getRGB(x,y));
    int red = col.getRed();
    return red;
  }

  public static int getGreenValue(BufferedImage img, int x, int y) {
    Color col = new Color(img.getRGB(x,y));
    int green = col.getGreen();
    return green;
  }

  public static int getBlueValue(BufferedImage img, int x, int y) {
    Color col = new Color(img.getRGB(x,y));
    int blue = col.getBlue();
    return blue;
  }

  public static void setColor(BufferedImage img, int x, int y, int r, int g, int b) {
    Color c = new Color(r, g, b);
    img.setRGB(x, y, c.getRGB());
  }