access to the way image is storeded?

Newbie & Debugging Questions
#1

Ok I know that the topic is a bit vague, but bear with me. I was wondering how can I get access to the raw data that an image is stored in on the hard drive. I am guessing that it is stored as a long list of hex values, but am prob wrong. Does anyone know exactly how the images is stored, and what the best way to access the raw data?

#2

If you have a BufferedImage image:

 byte[] data=((DataBufferByte)tex.getRaster().getDataBuffer()).getData()

Careful though you might need:

 int[] data=((DataBufferInt)tex.getRaster().getDataBuffer()).getData()

or you’ll get a ClassCastException. Try one, if you get the exception, try the other ;D

That’ll give you the pixel data in int’s or byte’s directly tied to the Image’s raster.

#3

great thanks.

Ok So I dont start a new thread, a quick question on dif topic:

If I write 1 byte of data to a file, it is stored as a 4kb file in Windows. I realize this is becasue of windows file structure, and am guessing that windows cannot have a file less than 4kb. Is this correct? can I store 1 byte into a file that takes up less than 4k on my windows machine?

#4

deends on the cluster size of your filesystem, but default is 4kb, yes.

#5

Ok back to the image question:

I created a 4 pixel image

R B
G G

when I get the byte array and display it I get the following
R 0 0 -2
B -4 0 1
G -1 0 3
G 3 -2 3

can anyone explain what this means? I was hoping to get values I can turn into binaries.

#6

Can you post the code, so we know what you are doing.

#7 
File f = new File("image\\pixels.jpg");
            BufferedImage src = javax.imageio.ImageIO.read(f);
      
            
            
            byte[] data=((DataBufferByte)src.getRaster().getDataBuffer()).getData() ;
            
            
            for (int i = 0; i < data.length; i++)
            {
                  System.out.print(data[i] + " ");
            }
#8

You don’t want to use “getRaster().getDataBuffer()).getData()” on images that are loaded from file. Atleast not if you are a newbie. The problem is that the image can be stored in so many different ways. Finding how it is stored and how to interprit it can be a hassle. It is mostly used on images that you create your self that you need speedy access too, like a software backbuffer. Since you create the image yourself, you know how the data is stored.

Use int[] BufferedImage.getRGB(int startX, int startY, int w, int h, int[] rgbArray, int offset, int scansize) instead. It creates a copy of the image, and it the data is always stored as argb (alphe, red, green, blue). Then you have to shift and mask to get what you want.