二次采样
需要加权限读写权限
//加载本地图片
BitmapFactory.Options options=new BitmapFactory.Options();
options.inJustDecodeBounds=true;
BitmapFactory.decodeFile("/storage/emulated/0/aaa.JPG",options);
//获取图片的宽高
int outWidth = options.outWidth;
int outHeight = options.outHeight;
//获取手机屏幕宽高
Display display = getWindow().getWindowManager().getDefaultDisplay();
int width = display.getWidth();
int height = display.getHeight();
//定义一个默认的比率值
int scale=0;
int scaleX=outWidth/width;
int scaleY=outHeight/height;
//得到一个大的比率值
scale=scaleX>scaleY?scaleX:scaleY;
//设置比例
options.inSampleSize=scale;
//加载图片内容
options.inJustDecodeBounds=false;
//按照比例进行压缩
Bitmap bitmap = BitmapFactory.decodeFile("/storage/emulated/0/aaa.JPG", options);
iv.setImageBitmap(bitmap);