Easiest way to convert RGB Color Image to Gray scale Image in Java

Hello GuyZ,
     I would like to share Java code to convert RGB images to Gray scale images. I have seen many Java codes which converts image to Gray scale by decomposing each pixel value to red, green and blue values. Then calculate (R+G+B)/3 and set this value to corresponding pixel.
     But I would like to share simplest code to convert color images to gray scale without calculations. The method I'm following is creating an Raster object, I'm using WritableRaster - because it allows reading and writing pixel values. Here I'm creating two WritableRaster objects - one for source image reading, second for writing pixels in output file.

WritableRaster wr = src.getRaster();
WritableRaster gr = gImg.getRaster();

Then using loop, read all pixels from source image and write it to output file. To read pixels, I used getSample(i, j, 0) function of WritableRaster, where i - column number, j - row number of pixel and 0 to get gray scale value for that pixel. After read gray scale value, set this value for output WritableRaster by using function, setSample(i, j, 0, gray_value). The gray_value is the value returned by getSample() function.

before converting to gray scale image

After converting to gray scale

Java Source Code

import java.awt.image.BufferedImage;
import java.awt.image.WritableRaster;
import java.io.File;
import javax.imageio.ImageIO;

/*
(C) AJITH KP (C) : TERMINALCODERS
*/

public class GrayscaleConversion {
    public static void main(String[] args) {
        System.out.println("#! TERMINALCODERS ::..\nhttp://www.terminalcoders.blogspot.com");
        if(args.length<2){
            System.out.println("Usage: java GrayscaleConversion <input file name> <output file name>");
        }
        else{
            try{
                File in = new File(args[0]);
                File out = new File(args[1]);
                BufferedImage img = ImageIO.read(in);
                BufferedImage gray = getGrayscaleImage(img);
                ImageIO.write(gray, "png", out);
                System.out.println("Grayscale image is saved in file: "+args[1]);
            } catch(Exception e){
                System.out.println(e);
            }
        }
    }

    private static BufferedImage getGrayscaleImage(BufferedImage src) {
        BufferedImage gImg = new BufferedImage(src.getWidth(), src.getHeight(), BufferedImage.TYPE_BYTE_GRAY);
        WritableRaster wr = src.getRaster();
        WritableRaster gr = gImg.getRaster();
        for(int i=0;i<wr.getWidth();i++){
            for(int j=0;j<wr.getHeight();j++){
                gr.setSample(i, j, 0, wr.getSample(i, j, 0));
            }
        }
        gImg.setData(gr);
        return gImg;
    }
    
}