認証コードなどのサムネイルの生成

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;

public class ThumbnailGenerator {
   
    public void transform(String originalFile, String thumbnailFile, int thumbWidth, int thumbHeight, int quality) throws Exception
    {
        Image image = javax.imageio.ImageIO.read(new File(originalFile));
       
        double thumbRatio = (double)thumbWidth / (double)thumbHeight;
        int imageWidth    = image.getWidth(null);
        int imageHeight   = image.getHeight(null);
        double imageRatio = (double)imageWidth / (double)imageHeight;
        if (thumbRatio < imageRatio)
        {
            thumbHeight = (int)(thumbWidth / imageRatio);
        }
        else
        {
              thumbWidth = (int)(thumbHeight * imageRatio);
        }
       
        if(imageWidth < thumbWidth && imageHeight < thumbHeight)
        {
            thumbWidth = imageWidth;
            thumbHeight = imageHeight;
        }
        else if(imageWidth < thumbWidth)
            thumbWidth = imageWidth;
        else if(imageHeight < thumbHeight)
            thumbHeight = imageHeight;

        BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics2D = thumbImage.createGraphics();
        graphics2D.setBackground(Color.WHITE);
        graphics2D.setPaint(Color.WHITE);
        graphics2D.fillRect(0, 0, thumbWidth, thumbHeight);
        graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);
       
        javax.imageio.ImageIO.write(thumbImage, "JPG", new File(thumbnailFile));
    }
}