ImageOp.java

import java.awt.image.*;
import java.awt.color.*;
import java.io.*;
import javax.imageio.*;


public class ImageOp {

public static BufferedImage readImage(String filename) {
	BufferedImage img = null;
       java.net.URL imgURL = ImageOp.class.getResource(filename);
	try {
        	if (imgURL != null) img = ImageIO.read(imgURL);
		else img = ImageIO.read(new File(filename));
	} catch (IOException e) {
		//System.out.println(e); // e.getMessage());
		System.out.println(filename + " not found");
		System.exit(-1);
	}
	return img;
    }

// convert rgb image to grayscale

public static BufferedImage rgb2gray(BufferedImage img) {
        int w1 = img.getWidth();
        int h1 = img.getHeight();
        // int value[][] = new int[w1][h1];
	int type = BufferedImage.TYPE_INT_RGB;
        BufferedImage gray = new BufferedImage(w1, h1, type);// new image
        int  v, r, g, b;
	int value[] = new int[w1];
        for (int j = 0; j < h1; j++) {

           img.getRGB(0, j, w1, 1, value, 0, w1); // read and store pixel value
       	   for (int i = 0; i < w1; i++) {
 		v = value[i];
                r = (v >> 16) & 0xFF;
                g = (v >> 8) & 0xFF;
                b = v & 0xFF;

                v = (r + g + b) / 3; // grey by averaging the pixels
		value[i] = 0xFF000000 | (v << 16) | (v << 8) | v;
            }
	    gray.setRGB(0, j, w1, 1, value, 0, w1);
        }
        return gray;
    }

// enlarges image by replicating pixels

public static BufferedImage replicate(BufferedImage img, int mag) {
         int w1 = img.getWidth();
         int h1 = img.getHeight();

	 int w2 = w1*mag;
	 int h2 = h1*mag; 
 	 int type = BufferedImage.TYPE_INT_RGB;
         BufferedImage out = new BufferedImage(w2, h2, type);
	 int [] value = new int[w1];
	 int [] vout = new int[w2];
	 int r = 0;
	 for (int j=0; j<h1; j++) {
          	img.getRGB(0, j, w1, 1, value, 0, w1); // read and store pixel value
		int c = 0;
		for (int i=0; i<w1; i++) {
			int v = value[i];
			for (int k=0; k<mag; k++) vout[c++] = v;
		}
		for (int k=0; k<mag; k++) out.setRGB(0,r++,w2,1,vout,0,w2);
	}
	return out;	
     }


}

Maintained by John Loomis, updated Tue Mar 03 20:48:00 2020