Problem with Slick 2d Image / Graphics

Newbie & Debugging Questions
#1

Hey, trying to create a simple new Image, blank, then add the graphics altered from another image and replace it with the image just made.

Sounds simple but when I’ve been trying to create a new image or even access any Images graphics its not been working, throwing a null error every time, real confused at this been wrecking my brain for past hour or two.

EDIT:
this is shader class with the problem in it:



package org.background.worker;

import java.util.Iterator;

import javax.swing.SwingWorker;

import org.background.LightProcessor;
import org.model.World;
import org.model.emitters.Emitter;
import org.model.emitters.Light;
import org.model.player.Player;
import org.newdawn.slick.Color;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.Image;
/**
 * Shader, for lighting.
 * @author Senior
 */
public class Shader extends SwingWorker<World, Void> {

	private LightProcessor processor = null;
	
	public LightProcessor getProcessor() {
		return processor;
	}

	public void setProcessor(LightProcessor processor) {
		this.processor = processor;
	}

	public Shader(LightProcessor processor) {
		this.setProcessor(processor);
	}

	@Override
	protected World doInBackground() throws Exception {
		if(processor.getWorld() == null) 
    		return null;
		World world = this.getProcessor().getWorld();
		Player player = world.getPlayer();
		if(player == null)
			return null;
		if(world.getLightEmitters().size() > 0) {
			for(Iterator<Emitter> it$ = world.getLightEmitters().descendingIterator(); it$.hasNext();) {
				Light l = (Light) it$.next();
				if(l == null)
					continue;
				if(!l.getPosition().isWithin(player.getPosition(), (int)l.getRange()))
					continue;
				if(player.getIcon() == null)
					continue;
				
				try {
					Image image = null;
					image = world.getBlank();
					if(image == null)
						continue;
					image = image.getScaledCopy(player.getIcon().getWidth(), player.getIcon().getHeight());
					if(image == null)
						continue;
					//Next line is problem line.
					Graphics g = image.getGraphics();
					if(g == null)
						continue;
					Image pixel = null;
					
					for(int h = 0; h < player.getIcon().getHeight(); h++) {
						for(int w = 0; w < player.getIcon().getWidth(); w++) {
							pixel = player.getIcon().getSubImage(w, h, 1, 1);
							g.drawImage(pixel, w, h, Color.red);
						}
					}
					
					player.setIcon(image);
				} catch(Exception e) {
					e.printStackTrace();
				}
			}
		}
		return world;
	}
	
}

In theory it should work but can’t find the graphics here is the error:


java.lang.NullPointerException
	at org.newdawn.slick.opengl.pbuffer.GraphicsFactory.init(GraphicsFactory.java:40)
	at org.newdawn.slick.opengl.pbuffer.GraphicsFactory.createGraphics(GraphicsFactory.java:120)
	at org.newdawn.slick.opengl.pbuffer.GraphicsFactory.getGraphicsForImage(GraphicsFactory.java:91)
	at org.newdawn.slick.Image.getGraphics(Image.java:397)
	at org.background.worker.Shader.doInBackground(Shader.java:62)
	at org.background.worker.Shader.doInBackground(Shader.java:1)
	at javax.swing.SwingWorker$1.call(Unknown Source)
	at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
	at java.util.concurrent.FutureTask.run(Unknown Source)
	at javax.swing.SwingWorker.run(Unknown Source)
	at org.background.LightProcessor.run(LightProcessor.java:37)
	at java.util.TimerThread.mainLoop(Unknown Source)
	at java.util.TimerThread.run(Unknown Source)

And here is where the Image ‘blank’ is set:


public World(Main main) {
		this.setMain(main);
		//Set up workers.
		this.setProcessor(new Processor(this));
		this.setLightProcessor(new LightProcessor(this));
		
		try {
			this.setBlank(new Image("./data/blank.png", false, Image.FILTER_LINEAR));
....
		} catch(SlickException e) {
			e.printStackTrace();
		}
	}

The world is initialized in the init() method of Main extends BasicGame.

Any ideas?

Peace.

#2

Is the image object null? If so it may not be finding the image. How are you loading the image?

#3

Was just trying to create a blank Image eg new Image(256, 256) to draw graphics on and create a image.
The image is throwing a null at the moment but the graphics also does.
I don’t get what’s happening the principle is simple.
I’ve tried numerous different ways, ImageBuffer, loading a actual Image it all seems to be obsolete.

http://img252.imageshack.us/img252/5395/codeerror.png

Peace

#4

I think the problem is in the constructor of Image() (in the backtrace you see org.newdawn.slick.Image.)

Are you sure player.getIcon().getWidth() and player.getIcon().getHeight() return the right size?

#5

Pretty sure and I’ve tried different constructors of Image and even images that I know work.
When I try get Graphics from the players icon that would throw a null too.

Even the graphics I use to paint the images if I try setting that and using it there it still doesn’t work.
Rather confusing me.

#6

This looks like an old LWJGL bug I’ve seen a while ago. Are you using the latest version?

#7

I thought I was I’ll download new LWJGL
Thanks mate.

#8

Well I updated my LWJGL from 2.8.3 - 2.8.4 and downloaded (newer?) version of Slick.
Still doesn’t work :confused:

http://img803.imageshack.us/img803/7501/errorreprt.png

Help?

#9

Is your OpenGL context created? I think with LWJGL you have to call Display.create(), but it is some time since I last used it.

Other thing I could think of is enabling textures in OpenGL:


import org.lwjgl.opengl.GL11.glEnable(GL11.GL_TEXTURE_2D);
#10

Tried both don’t seem to work.
This my initialize method;

http://img690.imageshack.us/img690/4665/initj.png

#11

Ooops, I forgot you are using Slick. I have never used it (except for the utils to load PNG textures).

Some random things that probably wont work (sorry :-():

  • Do you try to create the image AFTER this.getApp().start() is called?
  • The init() method is of a class inherited from org.newdawn.slick.BasicGame? Although I don’t think it’s relevant for this error, you could append the @Override tag to it, so you get a warning if it doesn’t override for some reason.
  • If your class is inherited from *.BasicGame, do you call the super() constructor on your constructor?
#12

Yeah I create after this.getApp().start() and the init method of that is not thats in Main which has the superclass BasicGame and it is calling Super(String).
Really not sure, if I was in java2d this would be easy.
But slick is awesome ¬.¬

#13

First of all I’d like to say that I’m a complete newbie. Perhaps that’s why I find something odd in the next piece of code:


try {
    Image image = null; 
    try {
        image = new Image(256,256);
    } catch (SlickException se) {se.printStackTrace();
}

//This is the line I'm talking about. What's the purpose of this?
image.getScaledCopy(player.getIcon.getWidth(), player.getIcon.getHeight());

Graphics g = image.getGraphics();
Image pixel = null;

You’re not setting another Image with the return of getScaledCopy(). Does this method sets ‘image’ to it’s scaled copy?

Anyway I don’t think it has something to do with your problem. But I do think that it might be a variable scope problem. Have you tried creating the ‘image’ outside the method and initializing it inside?

#14

Oh no that was an accident I forgot to put image = image.getScaledCopy().
Yeah the image I have tried that the image in first post is made in init().
Yet again I’m just not sure what’s going on, should be simple.

#15

You tried this:


public void init(){
    Image image;
}

public void render(Graphics g){
    image = new Image(256,256);
}

Or this (this is what I meant)


Image image;

public void init(){
    image = new Image(256,256);
}

public void render(Graphics g){
    image.resizeOrDrawThisImage();
}
#16

This is in render and the image is created in init()

http://img717.imageshack.us/img717/246/inrender.png

Window is crashed…

#17

It would help if you pasted your actual code instead of screenshots.

#18

Just rolled out of bed so I could be wrong/late.

Define the variable you’d like to use to connect a image to “Sprite”.
Define the image/path, than link it to that Sprite variable.
Than render that Sprite variable after linking the Image to it.

public BufferedImage Sprite;
public ImageIcon player = new ImageIcon("path/to/file.png");

	public void paint(Graphics g) {
		Sprite = player.getImage();
		g.drawIage(Sprite, 20, 20, null);
	}

Hope it helps some :slight_smile:

#19

Yeah just post an SSCCE please :slight_smile:

#20

Its slick not java 2d mate.

And i’ll edit my thread with sscce in a minute.

edit; updated.