大图片预防oom

package cn.hugo.android.scanner.common;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
public class BitmapUtils {

   public static Bitmap decodeSampledBitmapFromResource(Resources res,
         int resId, int reqWidth, int reqHeight) {

      // First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res, resId, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth,
reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
      return BitmapFactory.decodeResource(res, resId, options);
}

   public static int calculateInSampleSize(BitmapFactory.Options options,
         int reqWidth, int reqHeight) {
      // Raw height and width of image
final int height = options.outHeight;
      final int width = options.outWidth;
      int inSampleSize = 1;
      if (height > reqHeight || width > reqWidth) {

         // Calculate ratios of height and width to requested height and
         // width
final int heightRatio = Math.round((float) height
               / (float) reqHeight);
         final int widthRatio = Math.round((float) width / (float) reqWidth);
// Choose the smallest ratio as inSampleSize value, this will
         // guarantee
         // a final image with both dimensions larger than or equal to the
         // requested height and width.
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
}

      return inSampleSize;
}

   public static Bitmap getCompressedBitmap(String path) {
      BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);
options.inSampleSize = calculateInSampleSize(options, 480, 800);
options.inJustDecodeBounds = false;
      return BitmapFactory.decodeFile(path, options);
}
}