图片压缩保存读取操作

            //对图片进行压缩
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            //获取这个图片的宽和高
            Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/dcim/Camera/hello.jpg",options);//此时返回bm为空
            options.inJustDecodeBounds =false;
            //计算缩放比
            int be = (int)(options.outHeight / (float)200);
            if(be <= 0)
                 be =1;
            options.inSampleSize =be;
            //重新读入图片，注意这次要把options.inJustDecodeBounds设为false哦
            bitmap = BitmapFactory.decodeFile("/sdcard/dcim/Camera/hello.jpg",options);
            int w = bitmap.getWidth();
            int h=bitmap.getHeight();
            System.out.println(w+" "+h);
            myImageView.setImageBitmap(bitmap);


            //保存入sdCard
            File file2= new File("/sdcard/dcim/Camera/test.jpg");
            try {
             FileOutputStream out = new FileOutputStream(file2);
             if(bitmap.compress(Bitmap.CompressFormat.JPEG, 100, out)){
                 out.flush();
                 out.close();
             }
         } catch (Exception e) {
             // TODO: handle exception
         }

         //读取sd卡
            File file =new File("/sdcard/dcim/Camera/test.jpg");
            int maxBufferSize = 16 * 1024;

             int len = 0;
             ByteArrayOutputStream outStream = new ByteArrayOutputStream();
              BufferedInputStream bufferedInputStream;
             try {
                 bufferedInputStream = new BufferedInputStream(new FileInputStream(file));
                 int bytesAvailable = bufferedInputStream.available();
                 int bufferSize = Math.min(bytesAvailable, maxBufferSize);
                 byte[] buffer = new byte[bufferSize];
                 while ((len = bufferedInputStream.read(buffer)) != -1)
                 {
                     outStream.write(buffer, 0, bufferSize);
                 }
                  data = outStream.toByteArray();
                 outStream.close();
                 bufferedInputStream.close();

             } catch (FileNotFoundException e) {
                 e.printStackTrace();
             } catch (IOException e) {
                 e.printStackTrace();
             }