Java colour collision detection

Question

I am making a 2d platformer game that takes in several premade images of "levels" and randomly inserts them into a list. The game never ends so it just keeps adding more images as needed.

I am having a problem with the character moving between the images because when the guy reaches the end of one image, it throws:

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: Coordinate out of bounds!
at sun.awt.image.ByteInterleavedRaster.getDataElements(ByteInterleavedRaster.java:318)
at java.awt.image.BufferedImage.getRGB(BufferedImage.java:918)
at GamePanel.fall(run.java:197)
at run.actionPerformed(run.java:41)
at javax.swing.Timer.fireActionPerformed(Timer.java:313)
at javax.swing.Timer$DoPostEvent.run(Timer.java:245)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

But my picture is 1000 by 600 pixels wide and it says it goes out of range at 1000,413.

This is the code for the section with the error:

public void getActImg(){
    int tmp=0;
    for(int i=0;i<inUse.size();i++){
        tmp+=inUse.get(i).getWidth();
        System.out.println(imgPix);
        if(tmp/imgPix>=0){//int divide by width of all the pictures to find current img
            actImg=inUse.get(i);
            System.out.println(i);
            break;
        }
    }
}
public void fall(){
    if(posY+foot>getHeight()){
        die();
    }
    System.out.println((totDist+posX)%imgPix+","+(posY+foot));
    if(actImg.getImg().getRGB((totDist+posX)%imgPix,posY+foot)==Color.WHITE.getRGB()){
        posY+=vy;
        vy+=g;
        onGround=false;
    }
    else{
        onGround=true;
        if(vy>3){
            posY-=vy;
        }
        vy=0;
    }
}

I have searched the internet for any form of help but they only talk about how to insert gravity or use box collision. I have the gravity but do not understand box collision. That is why I am using colour. Any help would be greatly appreciated

Thank you

Vincent · Accepted Answer · 2015-05-01 20:58:30Z

1

Images are just like 2D arrays. The position (1000,413) IS outside the image, since indices start at 0 and go up to 999. When getting a color at a position, make sure the position is less than the width or height of the image, not less than or equal.

In public void fall():

int x = (totDist + posX) % imgPix; // NOTE: I am not sure what imgPix is or why you are modding the value by it.
int y = posY + foot;


if (x > 0 && x < actImg.getWidth() && y > 0 && y < actImg.getHeight()) {
    if (actImg.getImg().getRGB(x, y) == Color.WHITE.getRGB()) {
        posY += vy;
        vy += g;
        onGround = false;
    }
}

edited May 1, 2015 at 20:58

answered May 1, 2015 at 1:32

Vincent

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6 Comments

hyperneutrino Over a year ago

So you mean position < limit rather that position <= limit, correct?

Vincent Over a year ago

@JamesSmith yes, assuming position is the x or y value you are checking and limit is the width or height of the image

Collin Over a year ago

@Vincent Thank you for the help but I do not know how to modify the code to do this. can you please clear this up?

Vincent Over a year ago

@Collin I will add some code to my answer to clarify

Collin Over a year ago

@Vincent Sorry to bug you again but I found it. That was part of my problem and my math was off on how to find the active image

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