public class ThumbnailUtil {

    /**
     * @param filename 原始檔名
     * @param thumbWidth 縮圖寬度
     * @param thumbHeight 縮圖高度
     * @param quality 縮圖質量
     * @param outFilename 輸出檔名
     */
    public static void createThumbnail(String filename,int thumbWidth ,int thumbHeight,
            int quality,String outFilename) throws
 
 Exception{
        //載入圖片
        Image image = Toolkit.getDefaultToolkit().getImage(filename);
        MediaTracker mediaTracker = new MediaTracker(new Container());
        mediaTracker.addImage(image, 0);
        mediaTracker.waitForID(0);

        //調整縮圖大小
        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);
        }

        //繪製縮圖
        BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight,
                BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics2d = thumbImage.createGraphics();
        graphics2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        graphics2d.drawImage(image, 0, 0, thumbWidth,thumbHeight,null);

        //儲存
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outFilename));
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(thumbImage);
        quality = Math.max(0, Math.min(quality, 100));
        param.setQuality((float)quality/100.0f, false);
        encoder.setJPEGEncodeParam(param);
        encoder.encode(thumbImage);
        out.close();
    }
}