Problem saving an int array as an image in Java

Question

I am trying to manipulate an image by first manipulating its data elements as bytes, and the saving it back as a RGB. The image size is 320x320x3 (rgb).

import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.awt.image.DataBufferByte;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.nio.IntBuffer;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;

class sobel_java {
    public static void main(String args[]){
        
        BufferedImage image = null;
        try{
            image = ImageIO.read(new File("butterfinger.jpg"));
            final byte[] image_pixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
            final int image_height = image.getHeight();
            final int image_width = image.getWidth();
            System.out.println(image_height);
            System.out.println(image_width);
    
            BufferedImage out_image = new BufferedImage(image_width, image_height, BufferedImage.TYPE_INT_RGB);
            /* Create an int array that contains image_pixels. */   
            IntBuffer intBuf = ByteBuffer.wrap(image_pixels).order(ByteOrder.BIG_ENDIAN).asIntBuffer(); 
            int[] array = new int[intBuf.remaining()];
            intBuf.get(array);
            /* Write the int array to BufferedImage. */
            out_image.getRaster().setDataElements(0, 0, image_width, image_height, array);
            /* Save the image. */
            ImageIO.write(out_image, "jpg", new File("out.jpg"));
            
        
    }catch(IOException e){
        System.out.println(e);
    }
    }
}

In runtime, I get the following error,

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: arraycopy: last source index 77120 out of bounds for int[76800]
    at java.base/java.lang.System.arraycopy(Native Method)
    at java.desktop/sun.awt.image.IntegerInterleavedRaster.setDataElements(IntegerInterleavedRaster.java:425)
    at sobel_java.main(sobel_java.java:30)

Trying to access array element at index 77120 where as array has elements till 76800, you can try initialise array with length 77120 or more — sanjeevRm
– sanjeevRm, Commented Apr 3, 2021 at 1:18

rzwitserloot · Accepted Answer · 2021-04-03 01:14:58Z

1

You're using an int array. Each pixel takes up 4 bytes then; RGB covers 3 of em, and the 4th is discarded. That way, it's 1 int = 1 pixel, vs. some bizarro packing algorithm.

Fix it by not using int arrays, or by manually injecting a 4th ignored byte.

answered Apr 3, 2021 at 1:14

rzwitserloot

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