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

public class BufferedImageExample {

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

        String pathToTheOriginalImg = "d:\\before.jpg";
        String pathToTheResultImg = "d:\\after.jpg";

        BufferedImage bi = ImageIO.read(new File(pathToTheOriginalImg));

        try (ByteArrayOutputStream resultOutputStream = rescale(bi);
             OutputStream outputStream = new FileOutputStream(pathToTheResultImg)) {
            resultOutputStream.writeTo(outputStream);
        }
    }

    private static ByteArrayOutputStream rescale(BufferedImage bi) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();

        int originalWidth = bi.getWidth();
        int originalHeight = bi.getHeight();
        int type = bi.getType() == 0 ? BufferedImage.TYPE_INT_ARGB : bi.getType();

        //rescale 50%
        BufferedImage resizedImage = new BufferedImage(originalWidth / 4, originalHeight / 4, type);
        Graphics2D g = resizedImage.createGraphics();
        g.drawImage(bi, 0, 0, originalWidth / 4, originalHeight / 4, null);
        g.dispose();
        g.setComposite(AlphaComposite.Src);
        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        ImageIO.write(resizedImage, "jpg", baos);
        return baos;
    }
}