Bitmap压缩图片

   代码实现：

 public class MainActivity extends AppCompatActivity {

     private ImageView img;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         initView();
         //从资源文件中得到图片
         Bitmap rawBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.abc);
         // 得到图片原始的高宽
         int rawHeight = rawBitmap.getHeight();
         int rawWidth = rawBitmap.getWidth();
         // 新建立矩阵
         Matrix matrix = new Matrix();
         matrix.postScale(0.2f, 0.2f);

         Bitmap newBitmap = Bitmap.createBitmap(rawBitmap, 0, 0, rawWidth, rawWidth, matrix, true);
         BitmapDrawable bitmapDrawable=new BitmapDrawable(newBitmap);
         img.setImageDrawable(bitmapDrawable);
     }

     private void initView() {
         img = (ImageView) findViewById(R.id.img);
     }
 }