Thread: Get Pixel

Hello

I'm trying to write a minor "snake" clone; but I have some problems with the code

I want to retrieve a pixel at (x,y) and check its color; and according to my googling I should use g.getRGB(x,y), but I can't get it to work.

import java.applet.Applet;
import java.awt.*;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.image.BufferedImage;
 
import javax.swing.JFrame;
 
public class SnakeTest2 extends Applet {
  int gap = 3;
 
  int mx, my;
 
  Image buffer = null;
 
  int w, h;
 
  public static void main(String[] a) {
    JFrame f = new JFrame();
    f.setSize(258, 277);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.getContentPane().add(new SnakeTest2());
    f.setVisible(true);
  }
 
  public SnakeTest2() {
    setSize(258, 277);
    Dimension d = getSize();
    w = d.width;
    h = d.height;
    buffer = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
  }
 
  public void paint(Graphics g) {
	  Graphics screengc = null;
 
    screengc = g;
 
 
    g = buffer.getGraphics();
 
 
 
  	g.setColor(Color.BLUE);
	g.fillRect(0,0,250,250);
	g.setColor(Color.BLACK);
	g.fillRect(5,5,240,240);
 
 
  // I want to check if the color of pixel (x,y) = RED, how do I do it?
 
 
 
    screengc.drawImage(buffer, 0, 0, null);
  }
}

The reason I'm testing is for collisiontesting.

I'm not quite sure of how to approach the problem in any different way.

I was thinking that the performance of fetching data from one pixel and react on the result would be much better than to store an entire area in an array and try to keep track of which pixels are colored that way for example. If thinking of a snake clone and the snake being of length 150 pixels, that would mean at least 150 iterations to just make sure you haven't run into the snake each time you are to update one pixel, as compared to just checking one single pixel to see if it's black or not. And it also gets around the problem of trying to figure out what pixels a circel of size x would color.

But still, I would be happy to hear any good alternative solutions to this problem!

I tried to use the robot class; and it worked to some extent, the problem is that the robotclass only works if it's on top of the screen. I want to read the pixel of the active window. And yes; I can fetch the proper location, but if another window is on top of the app window, the robotclass doesn't do it.