Merge Multiple Images into One Image in Android

package com.example.android.imagemerger;

import java.util.ArrayList;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.GridView;
import android.widget.ImageView;

/**
 * @author Chandra Sekhar Nayak
 * @version 1.0 
 * 
 * This class is an activity and will displayed first when
 * application starts This Activity will display small images in a grid
 * view It also shows a button showing "Merge" on it. When clicks
 * merges the small image chunks
 */
public class SmallImagesActivity extends Activity implements OnClickListener {

    ArrayList<Bitmap> smallImages;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.image_grid);

        // This application will for merging number of smaller chunks to make
        // the original So for that we need some smaller image chunks. As I
        // don't have any smaller images, so I programmatically first split an
        // image to get the smaller image chunks and then merge them to get the
        // original one. If you want you can also get some smaller chunks and
        // directly merge them. The below 4 lines of code does the splitting
        // operation
        ImageView image = new ImageView(getApplicationContext());
        image.setImageResource(R.drawable.katewinslet);
        int chunkNumbers = 25;
        smallImages = splitImage(image, chunkNumbers);

        // This code is to show all the smaller image chunks into a grid
        // structure
        GridView grid = (GridView) findViewById(R.id.gridview);
        grid.setAdapter(new ImageAdapter(this, smallImages));
        grid.setNumColumns(5);

        // This gets the merge button and registers an click listener on it.
        Button mergeButton = (Button) findViewById(R.id.merge_button);
        mergeButton.setOnClickListener(this);
    }

    /**
     * Splits the source image and show them all into a grid in a new activity
     * 
     * @param image The source image to split
     * @param chunkNumbers The target number of small image chunks to be formed
     *            from the source image
     * @return ArrayList<Bitmap> The resulted smaller image chunks in a List of
     *         Bitmaps
     */
    private ArrayList<Bitmap> splitImage(ImageView image, int chunkNumbers) {

        // For the number of rows and columns of the grid to be displayed
        int rows, cols;
        rows = cols = 5;

        // For height and width of the small image chunks
        int chunkHeight, chunkWidth;

        // To store all the small image chunks in bitmap format in this list
        ArrayList<Bitmap> chunkedImages = new ArrayList<Bitmap>(chunkNumbers);

        // Getting the scaled bitmap of the source image
        BitmapDrawable drawable = (BitmapDrawable) image.getDrawable();
        Bitmap bitmap = drawable.getBitmap();
        Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, bitmap.getWidth(),
                bitmap.getHeight(), true);

        rows = cols = (int) Math.sqrt(chunkNumbers);
        chunkHeight = bitmap.getHeight() / rows;
        chunkWidth = bitmap.getWidth() / cols;

        // xCoord and yCoord are the pixel positions of the image chunks
        int yCoord = 0;
        for (int x = 0; x < rows; x++) {
            int xCoord = 0;
            for (int y = 0; y < cols; y++) {
                chunkedImages.add(Bitmap.createBitmap(scaledBitmap, xCoord, yCoord, chunkWidth,
                        chunkHeight));
                xCoord += chunkWidth;
            }
            yCoord += chunkHeight;
        }
        return chunkedImages;
    }

    /**
     * This method actually implements the code for merging the small images
     * @see android.view.View.OnClickListener#onClick(android.view.View)
     */
    @Override
    public void onClick(View view) {

        // Get the width and height of the smaller chunks
        int chunkWidth = smallImages.get(0).getWidth();
        int chunkHeight = smallImages.get(0).getHeight();

        // create a bitmap of a size which can hold the complete image after
        // merging
        Bitmap bitmap = Bitmap.createBitmap(chunkWidth * 5, chunkHeight * 5,
                Bitmap.Config.ARGB_4444);

        // create a canvas for drawing all those small images
        Canvas canvas = new Canvas(bitmap);
        int count = 0;
        for (int rows = 0; rows < 5; rows++) {
            for (int cols = 0; cols < 5; cols++) {
                canvas.drawBitmap(smallImages.get(count), chunkWidth * cols, chunkHeight * rows,
                        null);
                count++;
            }
        }

        // The result image is shown in a new Activity
        Intent intent = new Intent(SmallImagesActivity.this, MergedImage.class);
        intent.putExtra("merged_image", bitmap);
        startActivity(intent);
    }
}

Some Important points: