缩放图片并加载到内存中

/**

1. 图片的宽高

2. 获取手机屏幕的宽高

3. 计算合适的缩放比例

4. 显示缩放图片

*/

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.os.Bundle;
import android.view.Display;
import android.view.WindowManager;
import android.widget.ImageView;
public class MainActivity extends Activity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      ImageView iv = (ImageView) findViewById(R.id.iv);
      Options opt = new Options();
      //只拿图片的宽高，不加载图片
      opt.inJustDecodeBounds = true;
      BitmapFactory.decodeFile("/mnt/sdcard/dog.jpg",opt);
      //图片的宽高
      int pHeight = opt.outHeight;
      int pWidth = opt.outWidth;
      //获取手机屏幕的宽高
      WindowManager wm=(WindowManager)getSystemService(Context.WINDOW_SERVICE);
      Display display = wm.getDefaultDisplay();
      int sWidth = display.getWidth();
      int sHeight = display.getHeight();
      //计算合适的缩放比例
      int width = pWidth / sWidth;
      int height = pHeight / sHeight;
      int scale = 1;
      if (width >= height && width > 1) {
         scale = width;
      }else if(height > width && height >1) {
         scale = height;
      }
      //显示缩放图片
      opt.inJustDecodeBounds = false;
      //设置缩放的比例值
      opt.inSampleSize = scale;
      Bitmap bmp = BitmapFactory.decodeFile("/mnt/sdcard/dog.jpg",opt);
      iv.setImageBitmap(bmp);
   }
}