A simple image sprite generator in Java

For some time I have been playing around with writing games for Android. The game loads the graphics in form of image sprites, so I needed a way to easily stick several png images into one image. I though there would be tons of free applications available for this purpose, but I didn’t find any, so I decided to create my own sprite generator.

The code is short and simple. Please feel free to use it as you please! 🙂

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.*;

public class SpriteGenerator {

    public static void main(String[] args) throws IOException {

        if (args.length != 2)
        {
           System.out.print("Usage: SpriteGenerator {path to images} {output file}");
           return;
        }

        String imagePath = args[0];
        String outputFile = args[1];

        File imageFolder = new File(imagePath);
        File[] files = imageFolder.listFiles();

        // Read images
        ArrayList imageList = new ArrayList();

        for (File f : files)
        {
            if (f.isFile())
            {
                String fileName = f.getName();
                String ext = fileName.substring(fileName.lastIndexOf(".")+1,
                                     fileName.length());

                if (ext.equals("png"))
                {
                    imageList.add(ImageIO.read(f));
                }
            }
        }

        // Find max width and total height
        int maxWidth = 0;
        int totalHeight = 0;

        for (BufferedImage image : imageList)
        {
            totalHeight += image.getHeight();

            if (image.getWidth() > maxWidth)
                maxWidth = image.getWidth();
        }

        System.out.format("Number of images: %s, total height: %spx, width: %spx%n", 
                                      imageList.size(), totalHeight, maxWidth);


        // Create the actual sprite
        BufferedImage sprite = new BufferedImage(maxWidth, totalHeight, 
                                                      BufferedImage.TYPE_INT_ARGB);

        int currentY = 0;
        Graphics g = sprite.getGraphics();
        for (BufferedImage image : imageList)
        {
            g.drawImage(image, 0, currentY, null);
            currentY += image.getHeight();
        }

        System.out.format("Writing sprite: %s%n", outputFile);
        ImageIO.write(sprite, "png", new File(outputFile));
    }
}

Output from a run:


java -classpath {...classpath hell...} SpriteGenerator ./images ./sprite.png
Number of images: 10, total height: 640px, width: 34px
Writing sprite: /Users/peter/Development/Android/HappyFrog/gfx/sprite.png