android图片压缩

andriod提供了一些方法如下：
压缩图片质量:  
bitmap.compress(Bitmap.CompressFormat.JPEG, quality, fos);  
其中的quality为0~100, 可以压缩图片质量, 不过对于大图必须对图片resize  

这个是等比例缩放:
bitmap = Bitmap.createScaledBitmap(bitmap, width, height, false);

这个是截取图片某部分:

bitmap = Bitmap.createBitmap(bitmap, x, y, width, height);

这几个方法都是针对Bitmap的, 不过鉴于Bitmap可以从file中读取, 也可以写入file

这段代码很多网站都有转载，在这里是为了注释：较大的图片文件上传到服务器一般都需要压缩调整，保证数据通信的效率是最主要的。

//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();              }