Question

I am trying to access the pixels of image using method getRGB(). The image I use for this purose is 8-bit image i.e each pixel is represented by 8-bits, hence the possible values are 0-255.
the image I used was png 8-bit image hence the type ‘type_byte_indexed’

if (type == BufferedImage.TYPE_BYTE_INDEXED) { 
    System.out.println("type.byte.indexed");
    System.out.print(h+"   "+w);    

    sourceImage.getRGB(0, 0, w, h, rgbs, 0, w); //rgbs is integer array

    for (i = 0; i <10; i++) {
        System.out.print("   "+rgbs[i]);  
     }
    System.out.println("rgbs len: " + rgbs.length); 
}

The output of the for loop is something ilke:

-12048344   -12174804   -12048344   -12174804   -12174804 .......

I obtain the r,g,b components from it and store in array :

    Color c=new Color(rgbs[i]);
    r=c.getRed();
    g=c.getGreen();
    b=c.getBlue();

Now how do I combine again these values so that I can use the setRGB method? Like for 24 bit image we can use

int rgb=65536*pixel[i]+256*pixel[i+1]+pixel[i+2];

Answer 1

The documentation clearly states that the returned values are in ARGB-form:

Returns an array of integer pixels in the default RGB color model (TYPE_INT_ARGB) and default sRGB color space

You can access the underlying buffer (that contains indexed pixels) with

byte[] data=((DataBufferByte)bufferedImage.getRaster().getDataBuffer()).getData(0);