Android Bitmap压缩方式分析

private void calculateBitmapInSimpleSize() {
    Bitmap _bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.bg_homepage);
    getBitmapDatas(_bitmap);

    BitmapFactory.Options optioins = new BitmapFactory.Options();
    optioins.inJustDecodeBounds = true;
//    optioins.inPreferredConfig = Bitmap.Config.RGB_565;//11158560
    optioins.inPreferredConfig = Bitmap.Config.ARGB_8888;//22317120
    BitmapFactory.decodeResource(getResources(), R.drawable.bg_homepage, optioins);
    int reqWidth = optioins.outWidth;
    int reqHeight = optioins.outHeight;

    Log.w(TAG, "reqWidth = " + reqWidth);
    Log.w(TAG, "reqHeight = " + reqHeight);

    int inSampleSize = 1;
    final int widthRatio = Math.round((float)reqWidth / 100f);
    final int heigthRatio = Math.round((float) reqHeight / 100f);
    // 取最小值 这将保证压缩出来的图片大于或者等于请求的宽度或者高度
    inSampleSize = widthRatio > heigthRatio ? heigthRatio : widthRatio;
    Log.w(TAG, "first inSampleSize = " + inSampleSize);

    final int totalPixel = 100 * 100;
    final int totalReqPixel = reqWidth * reqHeight * 2;

    Log.w(TAG, "totalReqPixel = " + totalReqPixel);

    while (totalPixel / (inSampleSize * inSampleSize) > totalReqPixel) {
      Log.w(TAG, "totalPixel = " + (totalPixel / (inSampleSize * inSampleSize)));
      inSampleSize ++;
    }

    Log.w(TAG, "LastInSampleSize = " + inSampleSize);

    optioins.inJustDecodeBounds = false;

    Bitmap lastBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.bg_homepage, optioins);
    getBitmapDatas(lastBitmap);

    mImageView.setImageBitmap(lastBitmap);

  }

// 计算bitmap所占内存值
 public void getBitmapDatas(Bitmap bitmap) {
     Log.w(TAG, "Bitmap size = " + bitmap.getByteCount());
  }