/**
 * 
 * @param srcPath 原圖片地址
 * @param desPath 目標圖片地址
 * @param desFileSize 指定圖片大小,單位kb
 * @param accuracy 精度,遞歸壓縮的比率,建議小于0.9
 * @return
 */
 public static String commpressPicForScale(String srcPath,String desPath,
 long desFileSize , double accuracy){
 try {
 File srcFile = new File(srcPath);
 long srcFilesize = srcFile.length();
 System.out.println("原圖片:"+srcPath + ",大小:" + srcFilesize/1024 + "kb");
 //遞歸壓縮,直到目標文件大小小于desFileSize
 commpressPicCycle(desPath, desFileSize, accuracy);
 
 File desFile = new File(desPath);
 System.out.println("目標圖片:" + desPath + ",大小" + desFile.length()/1024 + "kb");
 System.out.println("圖片壓縮完成!");
 } catch (Exception e) {
 e.printStackTrace();
 }
 return desPath;
 }

 public static void commpressPicCycle(String desPath , long desFileSize,
 double accuracy) throws IOException{
 File imgFile = new File(desPath);
 long fileSize = imgFile.length();
 //判斷大小,如果小于500k,不壓縮,如果大于等于500k,壓縮
 if(fileSize <= desFileSize * 500){
 return;
 }
 //計算寬高
 BufferedImage bim = ImageIO.read(imgFile);
 int imgWidth = bim.getWidth();
 int imgHeight = bim.getHeight();
 int desWidth = new BigDecimal(imgWidth).multiply(
  new BigDecimal(accuracy)).intValue();
 int desHeight = new BigDecimal(imgHeight).multiply(
  new BigDecimal(accuracy)).intValue();
 Thumbnails.of(desPath).size(desWidth, desHeight).outputQuality(accuracy).toFile(desPath);
 //如果不滿足要求,遞歸直至滿足小于1M的要求
 commpressPicCycle(desPath, desFileSize, accuracy);
 }

commpressPicForScale(filePath, filePath, 500, 0.8);