How to write a grayscale image from a 2D array

Question

I wanted to read a grayscale image values into a 2d array, change the values of the 2d array and create a new grayscale image from the modified values of 2d array.

Following is the code to read the grayscale image into 2D array(arr[][]).

package dct;

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

/**
 *
 * @author jain
 */
public class writeGR {

            public static void main(String[] args)
            {
                File file = new File("lightning.jpg");
                BufferedImage img = null;
                try
                {
                    img = ImageIO.read(file);
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }

                int width = img.getWidth();
                int height = img.getHeight();
                int[][] arr = new int[width][height];

                Raster raster = img.getData();

                for (int i = 0; i < width; i++)
                {
                    for (int j = 0; j < height; j++)
                    {
                        arr[i][j] = raster.getSample(i, j, 0);

                    }
                }

                BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
                image.setData(raster);
                //
                //BufferedImage image1 = image;
                try
                {
                    File ouptut = new File("grayscale.png");
                    ImageIO.write(image, "png", ouptut);
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }    

        }// main

}

Now I want to change the "arr[][]" vlaues and create a new grayscale image out of that. How to do this?

If you want to change the values of arr, just loop through them again as you did before and say for instance: `arr[i][j] = arr[i][j]/2;` — Roel Strolenberg, Jun 23 '15 at 08:26
@Roel - Assume I did "arr[i][j] = arr[i][j]/2;" . Now how to write the image with new "arr[][]" values?? — Rohit S, Jun 23 '15 at 09:02
http://stackoverflow.com/questions/14416107/int-array-to-bufferedimage explains how to go from int[][] to bufferedImage. Then just save the image =) — Roel Strolenberg, Jun 23 '15 at 09:33

score 0 · Answer 1 · answered Jun 23 '15 at 09:32

The above problem can be solved by the following code:

                for(int i=0;i<width;i++)
                {
                    for(int j=0;j<height;j++)
                    {
                        tempArr[0] = 100;
                        raster1.setPixel(i, j, tempArr);
                    }
                }

                BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
                image.setData(raster1);

                try
                {
                    File ouptut = new File("change.png");
                    ImageIO.write(image, "png", ouptut);
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }

How to write a grayscale image from a 2D array

1 Answers1