尺寸不變，大小壓縮

  public static boolean compressPic(String srcFilePath, String descFilePath) throws IOException {
        File file = null;
        BufferedImage src = null;
        FileOutputStream out = null;
        ImageWriter imgWrier;
        ImageWriteParam imgWriteParams;

        // 指定寫圖片的方式為 jpg
        imgWrier = ImageIO.getImageWritersByFormatName("jpg"
 
).next();
        imgWriteParams = new javax.imageio.plugins.jpeg.JPEGImageWriteParam(
                null);
        // 要使用壓縮，必須指定壓縮方式為MODE_EXPLICIT
        imgWriteParams.setCompressionMode(imgWriteParams.MODE_EXPLICIT);
        // 這裡指定壓縮的程度，引數qality是取值0~1範圍內，
        imgWriteParams.setCompressionQuality((float
 
)1);
        imgWriteParams.setProgressiveMode(imgWriteParams.MODE_DISABLED);
        ColorModel colorModel = ImageIO.read(new File(srcFilePath)).getColorModel();// ColorModel.getRGBdefault();
        // 指定壓縮時使用的色彩模式
//        imgWriteParams.setDestinationType(new javax.imageio.ImageTypeSpecifier(
//                colorModel, colorModel.createCompatibleSampleModel(16, 16)));
 

        imgWriteParams.setDestinationType(new javax.imageio.ImageTypeSpecifier(
                colorModel, colorModel.createCompatibleSampleModel(16, 16)));

        try {
            if (isBlank(srcFilePath)) {
                return false;
            } else {
                file = new File(srcFilePath);
                System.out.println(file.length());
                src = ImageIO.read(file);
                out = new FileOutputStream(descFilePath);

                imgWrier.reset();
                // 必須先指定 out值，才能呼叫write方法, ImageOutputStream可以通過任何
                // OutputStream構造
                imgWrier.setOutput(ImageIO.createImageOutputStream(out));
                // 呼叫write方法，就可以向輸入流寫圖片
                imgWrier.write(null, new IIOImage(src, null, null),
                        imgWriteParams);
                out.flush();
                out.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    public static boolean isBlank(String string) {
        if (string == null || string.length() == 0 || string.trim().equals("")) {
            return true;
        }
        return false;
    }