A noobish question about loading BufferedImage

Newbie & Debugging Questions
#1

Hi all just a quick questiong :slight_smile:

I understood that we can only load BufferedImages with ImageIO.read( url ) ; , right?

Thing is I have no idea about URL so I took only the example from the Planetalua space invaders tutorial and made the URL like this :
url = getClass().getClassLoader().getResource(filename);

Thins is , ok it works … but what If I wan tto have my images in another place and not in the classloader?How do I form my own URL to tell it where to load the images from?

I tried URL url = new URL( String string) ;

But it said something about malfunctioned URL and about a protocol.Please excuse my noobiness :frowning: , and any help is appreciated ! :smiley:

#2

ImageIO’s read() method is also available as a version which takes an InputStream.

but what If I wan tto have my images in another place and not in the classloader?

Why?

#3

hmm don’t know why , I just want toexplore all my options I guess.Hm did not know it can take InputStream too … need to studdy the API’s better I guess :-X

EDIT: Another question arose … I reread the tutorial to help me divide the code in classes and I made the SpriteCache class like in the tutorial :

package Version01;

import java.awt.image.BufferedImage;
import java.util.HashMap;
import java.net.URL;
import javax.imageio.ImageIO;

public class SpriteCache
{
    private HashMap sprites;
    private URL url;
    
    public SpriteCache()
    {
        sprites = new HashMap();
    }
    
    private  BufferedImage loadImage(String filename)
        {
           
            try
            {
                url = getClass().getClassLoader().getResource(filename);
                return ImageIO.read(url);
            }
             catch(Exception e)
             {
                 e.printStackTrace();
                 return null;
             }
        }
    
    
    public BufferedImage getSprite(String name)
    {
        BufferedImage img = (BufferedImage)sprites.get(name);
        if(img == null)
        {
            img = loadImage("images/"+name);
            sprites.put(name , img);
        }
        return img;
    }
}

Thing is in my main class … in the paintWorld() method I try to load an image in a random position of the screen


public void paintWorld()
    {
        Graphics2D g = (Graphics2D) strategy.getDrawGraphics();
        g.setColor(getBackground());
        testImage = spriteCache.getSprite("test.gif");
        g.drawImage(testImage , 80 , 90 , this);
        strategy.show();
    }

When I run it it throws a NullPointerException … :frowning: seems it can not find the image … I am sure the image has the right name though and is at the right place.So what is wrong with the code?

#4

Sorry about double posting , but I bump my thread cause I edited the above reply of mine with another question

#5

Uhm yea… use leading slashing in the path for making it relative to the roots in the classpath.

say your jar contains:
omg/wtf/Foo.class
omg/Bar.class
gfx/foobar.png

and another jar in your cp contains:
gfx/barfoo.png

Then you can access the foobar.png with “/gfx/foobar.png” and barfoo.png with “/gfx/barfoo.png” from Foo.class or Bar.class.

Thats the whole magic :slight_smile:

edit: See details here:
http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Class.html#getResource(java.lang.String)

#6

Hmmmm If I understood correctly all I had to do was add a / at the “images/”+name ?

I did that but it did not work :frowning:

Or again I might have completely misunderstood :stuck_out_tongue: , it is 2:00 here in Greece and I am kind of sleepy ; (

#7

Well, whats the location of that test.gif? (Note that the whole thingy inclusive the extension is case sensitive)

#8

C:\Java2\Game\build\classes\images\test.gif

That is where it is … but I don’t think it is that kind of mistake because I move the images folder and recompiled and ran many many times.

#9

http://kaioa.com/k/jarimage.jar

Comes with source. Its double clickable and it also works in extracted form.

#10

Thanks for even going through the trouble of doing that ;D

I have no idea what iw wrong with my code so … all I can do is rewrite it now that it is morning … the sun is shining outside … the coffe is plenty e.t.c. :wink:

Also thanks again again and again for striving to answer every single question :smiley: