Android之从SD卡加载大图片

public class MainActivity extends Activity {

/*
* 从SD卡里加载图片
*/
private ImageView iv;
public void loadImage(View view) {
// TODO Auto-generated method stub
if (Environment.getExternalStorageState().
equals(Environment.MEDIA_MOUNTED)) {
//路径
String path=Environment.getExternalStorageDirectory()+
"/img_big_1.jpg";
//获取屏幕的宽，高
WindowManager windowManager=(WindowManager) getSystemService(WINDOW_SERVICE);
//			int screenWidth=windowManager.getDefaultDisplay().getWidth();
//			int screenHeight=windowManager.getDefaultDisplay().getHeight();//过时了
Display display=windowManager.getDefaultDisplay();
Point point=new Point();
display.getSize(point);
int screenWidth=point.x;
int screenHeight=point.y;
System.out.println(screenWidth);
System.out.println(screenHeight);

//获取原图的宽高
try {
ExifInterface exifInterface=new ExifInterface(path);
int imageWidth=exifInterface.getAttributeInt(ExifInterface.TAG_IMAGE_WIDTH, 0);
int imageHeight=exifInterface.getAttributeInt(ExifInterface.TAG_IMAGE_LENGTH, 0);
int sampleWidth=(int)(imageWidth*1.0f/screenWidth+0.5f);//加0.5就是为了四舍五入
int sampleHeight=(int)(imageHeight*1.0f/screenHeight+0.5f);
int sample=(int)(Math.sqrt(sampleWidth*sampleWidth+sampleHeight*sampleHeight)+0.5f);

Options options=new Options();
//设置图片的采样率
//options.inSampleSize=4;//原宽*1/4   原高*1/4
options.inSampleSize=sample;
//Bitmap bitmap=BitmapFactory.decodeFile(path);
//iv.setImageBitmap(bitmap);
Bitmap bitmap=BitmapFactory.decodeFile(path,options);
iv.setImageBitmap(bitmap);

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
iv=(ImageView) findViewById(R.id.iv);
}
}

<uses-permission android:name="android.permission.MEDIA_CONTENT_CONTROL"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>